Chloe Anne Sullivan was born in Metropolis in early 1987. Chloe's parents divorced when she was young. Her mother first left the family when Chloe was five, but Chloe had at least some contact with her mother until age eight in 1995. Chloe and her father, Gabe Sullivan, moved to Smallville in 2000, where Chloe quickly befriended Clark Kent and Pete Ross.
In Season One... Chloe was a reporter and the editor for her pride and joy, the Smallville Torch, the newspaper at Smallville High School, which she attended with Clark and Pete. At the Torch office, she maintained the “Wall of Weird,” a large mural where she posted articles concerning the often bizarre and eerie events that take place in Smallville, many of which are related to the mutagenic effects of the kryptonite from the 1989 meteor shower. Chloe seemingly had 24-hour access to the Torch office and a computer set aside for her personal use.
With contacts at the police station, public records, as well as even local hospitals and morgues, Chloe became Clark's source of information when it came to stopping meteor freaks determined to achieve their goals at the expense of hurting people. Many of these meteor freaks were students at Smallville: as a result, the victims were often classmates. Chloe was no exception and had several dangerous encounters in her freshman year.
From the start of the season, it was clear that Chloe had feelings for Clark, and had for a long time. However, Clark seemed to be oblivious to her affection and thought of her only as his best friend. Chloe was too scared of being rejected by Clark to confess her feelings for him, so she continually pushed them down, even going so far as to advise and help Clark with his pursuit of Lana Lang, albeit with more than a little reluctance at times. Despite her jealousy, Chloe actually became good friends with Lana.
Clark decided to explore the possibility of a relationship with Chloe by asking her to their Spring Formal. Chloe happily accepted, and they attended the dance together. They very nearly shared a kiss on the dance floor, but the moment was ruined by a series of tornadoes hitting Smallville. Clark left Chloe at the dance to go and rescue Lana, fulfilling in this way Chloe’s fear of being abandoned by him.
In Season Two... Hurt that Clark had left her at the dance to go to Lana's aid, Chloe told Clark that they should go back to being just friends. She was disappointed when Clark agreed easily, but went back to pushing aside her feelings for him. Chloe spent her summer vacation as an intern at The Daily Planet in Metropolis.
When she returned to Smallville for her sophomore year, she assured Clark that she completely over everything that happened, although she still had hurt feelings. Chloe was also jealous of the growing relationship between Lana and Clark, which had arisen in her absence.
Chloe continued to help Clark stop the meteor-infected in Smallville, although her jealousy and hurt caused her to push the boundaries of their friendship more than once. She and Clark had their first serious fight when he discovered that she had been investigating his adoption even though she had promised him she would not. The fight was mediated by Lana, and they eventually made up.
Chloe continued to grow closer to Lana, and even invited her to move in when Lana's aunt decided to move to Metropolis. They cultivated a sister-like friendship, despite their issues with Clark which caused the occasional rift between them. Chloe even chose to include Lana on her family tree as her sister, stating that her family tree should contain people who love her, not people who aren't there.
When Clark became infected with kryptonite spores, Chloe went to visit him at home. While he was unconscious, she read him an emotional, heartfelt letter detailing her feelings for him. However, Clark muttered Lana's name in his sleep and Chloe left heartbroken.
Towards the end of sophomore year, an estrangement developed between Clark and Chloe. Clark forgot to write an article for the Torch because he was doing a favor for Lana. Chloe accused him of never being there when she needed him and he accused her of acting as if he was cheating on her whenever he was around Lana. She denied this and the bitter argument that ensued caused both of them to take a break from their friendship.
Later on, the Torch office was severely vandalized, leaving Chloe devastated. She was approached by Lionel Luthor, who was becoming increasingly obsessed with the mysterious circumstances surrounding Clark. Lionel offered to restore the Torch office and also offered Chloe a job at the Daily Planet - her own column, entitled Sullivan's Travels. Although he kept his promise and repaired the office damage, Chloe turned him down when she realized he also wanted her to investigate Clark.
Although Chloe and Clark were mending their broken friendship, at the same time Clark and Lana began a romantic relationship behind her back. Both were hesitant to reveal their new status to Chloe, and when Chloe found eventually out on her own she was furious and heartbroken. Deeply hurt by their betrayal, Chloe decided not to them that she had discovered their relationship, to see how long it would take them to actually be honest with her. But she eventually confronted Clark with it and ended their friendship once again. And, rather than warn Clark about Lionel as she initially planned, Chloe accepted Lionel's deal, agreeing to investigate Clark in exchange for the job at the Daily Planet.
In Season Three... Working in Metropolis at the Daily Planet, Chloe ran into Clark, who had ran away from home and taken the name Kal, but promised not to reveal where he was, mostly because he threatened her. She approached him again and pleaded with him to come home, but Kal reacted violently and dangerously. She told Lana where Clark was and Lana got upset with her for keeping it a secret.
Clark and Chloe both returned to Smallville for their junior year of high school. Their relationship was still strained however, due to Clark's unexplained behavior over the summer and the fact that Chloe was still investigating Clark for Lionel Luthor. She eventually decided that she didn't want to do so anymore, but Lionel refused to allow her out of their deal and threatened her.
During this time, Perry White came to Smallville and asked Clark to take him to meet the editor of the Torch who had “a reputation among the bug-eyed monster circles.” Chloe was eager to talk about her Wall of Weird, and thrilled to meet the Perry White: multiple Pulitzer-nominated journalist extraordinaire.
Chloe saw a possible way out of her deal with Lionel when Clark asked her help to investigate the truth about a mystery involving Lex Luthor’s grandfather and Lana’s great aunt. She discovered that Lionel probably killed his parents to claim the insurance. Chloe began her own investigation into Lionel, intending to bring him down once and for all. Lex eventually discovered her deal with his father and her investigation, and warns her about the dangers of crossing his father. They decided to team up and bring Lionel down together.
When Lionel discovered Lex and Chloe's attempt at bringing him down, he accused Lex of insanity and submitted him to a radical electroshock therapy that made him forget his deal with Chloe and what they found out about Lionel's conspiracy to kill his parents.
Lionel demanded another report on Clark, and reminded Chloe that Lex couldn't help her anymore. She became very scared and after Clark, using his newly acquired super-hearing, accidentally overheard the telephone conversation between her and Lionel, she assured him that she didn't tell Lionel anything he didn't already know and pleaded for forgiveness, but Clark did not accept her apology and their friendship was tenuous for a time. Chloe promised Clark she would stop investigating him, and when she wouldn't comply with Lionel's demands he canceled her Daily Planet column, and made Lex fire her father from his job.
To prevent Chloe from writing an exposé, an employee at The Summerholt Institute sent out hypnotic emails to Chloe's friends. Clark and Lana each attempted to kill Chloe and she took refuge in Lex's mansion. Later, Chloe confessed to Clark that maybe she deserved it and Clark decided that if Chloe forgave him for trying to kill her, he could forgive her for investigating his past. He gave her a second chance because she gave him one when he once made a bad choice at a moment of weakness. He told her that he knows things won't make sense or add up about him, and she told Clark that she realizes he'll tell her his secret when he's ready.
When Chloe was exposed to a kryptonite-based truth agent at LuthorCorp, she momentarily obtained the ability to make anyone tell her the truth, except for Clark, but she threatened to discover his secret. Chloe tore through Smallville making Martha Kent, Lex, Lana, as well as others tell her their private thoughts and in the process, setting off an avalanche of unfortunate events. Chloe found the perfect opportunity to take down Lionel and tried to record Lionel confessing to killing his parents in order to blackmail him into hiring her father back: Lionel, however, later hacked her voice-mail and deleted his confession.
Chloe told Lex what had happened with Lionel during the time he couldn't remember, and they reformed their partnership. The data of Lionel's confession was retrieved and a transcript was made. Before going to testify against Lionel, Chloe and her father were taken to a witness-protection safe house. However, moments after stepping in the door, the house was blown up by an explosion and Chloe was presumed dead.
In Season Four... Chloe's cousin Lois Lane came to Smallville to find out the truth about her death. She and Clark began investigating Chloe's apparent murder, but discovered that she was actually alive. Lex told Clark how he saved her and her father from the blast and faked their deaths to prevent Lionel from finding them. Her testimony, and the voicemail confession, helped convict Lionel of the murder of his parents, landing him in prison.
Chloe returned to Smallville High to complete her senior year of high school, joined by her cousin, Lois Lane. It was discovered that Lois was actually a few credits short of graduating high school, and therefore cannot continue on to college until she completes them. Although Chloe was very close to her cousin and was happy to have her there, she struggled with some feelings of jealousy when she saw the sparks between Lois and Clark. She was, however, thrilled when Lois begins writing for the Torch, as Lois' curious and intrepid nature matched her own.
When Chloe accidentally drank a kryptonite-enhanced love potion she became desperately devoted to Clark, pursuing him aggressively and relentlessly. After the effects wore off she was embarrassed by her behavior, and Clark told her that he didn't have romantic feelings for her. They remained friends, and although it was clear that Chloe did still have lingering feelings for Clark, it was a turning point in their friendship, with Chloe finally laying her hope for a romantic relationship with Clark to rest.
When Lana confided in Chloe that she was considering having sex with her boyfriend, Jason Teague, Chloe confessed to Lana that she had lost her own virginity during her summer internship at The Daily Planet, with a boy named Jimmy. She advised Lana to make sure that she was ready, and that Jason was the one she wanted to remember forever, because she sometimes regretted her own decision.
On her eighteenth birthday, Chloe, Lana, and Lois were possessed by three 17th Century witches. They attacked Clark and stripped him of his powers, however he eventually overcame them, and all three girls were returned to normal with no memory of what had happened.
Around this time, Chloe began to seriously suspect that something was different about Clark. However, instead of meddling or investigating as a younger Chloe might have done, she simply stepped back and hoped Clark would trust her enough to tell her himself. Chloe confided in Clark, revealing to him that she had found her mother in a mental hospital three months ago, being treated for a hereditary mental illness, which Chloe feared she could one day inherit. She emphasized that she felt much better having shared her secret with someone.
Shortly after, Chloe truly learned of Clark's powers from a “demonstration” arranged by Alicia Baker, in which she saw Clark catch a car, then super-speed away unknowingly revealing his super-strength and super-speed. She believed Clark to be a meteor freak from the meteor shower, like Alicia. After seeking advice from Lois, without revealing Clark's secret, Chloe decided not to tell Clark what she knew and continued to be the same good friend she always had been, waiting for him to tell her when he was ready. However, she frequently dropped subtle hints urging Clark to tell her.
Once Chloe had discovered the secret of her best friend, she became his best ally, although he was often unaware of this. She became fiercely loyal to him and began making excuses to cover up his mysterious disappearances. Gradually, Chloe was discovering in secret the rest of Clark's powers while continued to support him in his research about the Stones of Power.
Chloe was reluctantly nominated as a candidate for Prom Queen their senior year and her main competition was Dawn Stiles, the most popular girl in school. The night of the Prom, Dawn was seriously injured in a car accident, but her spirit remained behind, jumping from body to body. When Chloe won, Dawn possessed Chloe and attempted to burn down the school. When Clark tried to stop her, Dawn jumped into him and as Jonathan Kent had to use kryptonite to subdue her spirit and free Clark, Chloe discovered that Clark was vulnerable to the meteor rock.
After Clark was struck with total amnesia, Chloe found herself teaching Clark about his own powers and learning about the ones of which she was not yet aware. She told him that she believed he was a meteor freak and that she had known about his secret without him telling her, instead trusting that he would confide in her on his own time. When Clark regained his memory, he asked what he had done during the time and Chloe simply told him he did one thing differently--he trusted her. She again left it open for Clark to tell her himself.
As senior year came to an end, Chloe sadly had to say goodbye to her years at the Torch. The graduation ceremony was interrupted when the military announced a second meteor shower on its way to Smallville. Chloe later discovered a kryptonite-weakened Clark in Lex's walk-in safe and pulled him to safety. When Lex found her in his office, he dragged her forcibly to the Kawatche Caves and demanded she give him answers. Chloe knocked him out and watched as Clark entered a chamber that mysteriously opened in the far wall.
In Season Five... Chloe and Clark were transported to the Fortress of Solitude in the Arctic, and unable to withstand the sub-zero temperatures, she called out to Clark, who begged to interrupt his training to save her life. Clark took Chloe to a hospital in the Yukon and Chloe finally told Clark that she knew his secret and Clark told her that he is an alien. She became his confidante, promising to never be the “iceberg to his Titanic.” Later, Lex located her and took her back to Smallville.
After Jor-El stripped Clark of his powers and Clark became mortal, Chloe was disappointed that now that Clark could finally be open with her about his abilities, he no longer had them. But since Clark was happy that he was finally normal, and finally in a relationship with Lana, she supported him. When Clark's family was held hostage by deranged meteor freaks, the now mortal Clark turned to Chloe's resourcefulness and cleverness. Together, they retrieved a kryptonite serum from Level Three at LuthorCorp plant without his abilities.
When Gabriel Duncan attempted to blow up Smallville with a nuclear missile, she and Clark confronted him and he shot and killed Clark, and took Chloe to his bunker for safety. However, Jor-El brought Clark back to life and restored his powers and he stopped the missile from landing. Clark's death and resurrection was not without a price. Clark returned to his former life of keeping secrets. Chloe urged him to tell Lana the truth, but he did not take her advice.
Chloe moved into the Metropolis University dorms and scared her first roommate away with a mini version of the Wall of Weird. Lana became her new roommate after applying for late acceptance.
Chloe became one step closer to her dream job of editor of the Daily Planet when she wrote a paper detailing her experiences with a vampire sorority. Chloe went undercover along with Lois to investigate the murder of stripper and wrote a story about it, and obtained her first byline, which Lois and Clark applauded her for.
Chloe revealed to Mr. and Mrs. Kent that she knew of Clark's abilities as she helped them to deal with Clark after he was infected with silver kryptonite. After Jonathan passed away, Martha told Chloe that she was glad she was not the only person carrying such a burden, saying that Clark was lucky to have Chloe as a friend.
After Clark and Lana broke up, Clark would frequently ask Chloe about Lana's well-being, until finally Chloe told him that she would rather not be in the middle. Chloe was the first to discover Lex and Lana's relationship and was shocked. Chloe and Lana had a fight when she questioned Lana's growing relationship with Lex. Both Lana and Lex responded to her questions with indignation, telling her to mind her own business. When Clark discovered the relationship, he became angry at her too, saying she betrayed him. Chloe stood up for herself, telling Clark that Lana can date whomever she chooses and suggesting he finally get over Lana. He later apologized when he realized that she was just being a good friend for keeping Lana's confidence.
After Lionel revealed that he had become Jor-El's oracle and had been producing pages and pages of scribbled Kryptonian characters. Chloe used her computer skills to decipher the characters into a readable sentence. Clark was then able to read it and translated it as “Zod is coming.”
When Professor Fine, who was revealed to really be Brainiac, downloaded a powerful virus into the electrical systems of the world, Clark went to help Chloe, but she told him that he had to leave her behind, because he couldn't save everyone. Before he left, Chloe gave him a passionate kiss, in case they “never see each other again.” Chloe watched riots breaking out in the streets of Metropolis but escaped into Lionel Luthor's limousine. Unfortunately, the limo was attacked by an angry mob and she and Lionel were pulled out of it.
In Season Six... Lionel rescued Chloe and they made their way to the LuthorCorp building. Once the power was returned and the virus was neutralized, Clark returned to her and offered to talk about the kiss they shared. Chloe claimed it did not change their friendship, leaving Clark seeming somewhat disappointed. She reunited with Jimmy Olsen, whom she had met and had fling with during her internship at The Daily Planet. They decided to rekindle their romance, but take it a little slower this time.
When Clark caught a cold in the Phantom Zone, Chloe convinced Clark to hone his sneezes into a useful new ability. Chloe also helped Clark and Lois try to learn the identity of the new hero in town, Green Arrow, who she really admired because of his ideals. She soon realized that Clark knew who he was, and stopped investigating when he asked her to.
On Thanksgiving Day, Lana confessed to Chloe that she was pregnant. Chloe attended the Kent Thanksgiving dinner, but did not tell Lana's secret. Shortly after, Lana enlisted Chloe and Jimmy to help her release Lex from an alternate frequency. Chloe hacked into Lex's computer and obtained schematics and floor plans for Level Three. However, once they rescued Lex, Chloe found all of her files deleted, with Lionel Luthor warning her to stop snooping. Lana did not believe Chloe when she told her about the Luthors' suspicious behavior.
Lana told Chloe that Lex proposed to her and admitted that she still has feelings for Clark. Clark found out Lana was pregnant and was angry at Chloe for not telling him, but Chloe got upset with him, stating that she has to keep other people's confidence as well as his, and they quickly made up. Lana later asked Chloe to tell her the truth about Clark, and his secret, but Chloe refused.
Chloe eventually figured out that Lois' boyfriend, Oliver Queen, was Green Arrow, and confessed to him that she had. Oliver saw her potential as part of his team and she took the codename Watchtower.
Lana asked Chloe to be her Maid of Honor, but a red kryptonite-infected Clark crashed the engagement party and said rude things to Chloe. Jimmy later confronted Chloe about the incident and wanted to know why she always defended Clark's actions and if she'd rather be with Clark than him. Chloe assured Jimmy that she was only interested in a relationship with him and that she defended Clark because there was more to Clark than Jimmy knew. Despite Chloe's assurances, Jimmy broke up with her.
At Lana's bachelorette party, Chloe witnessed a meteor freak get abducted. She and Clark investigated his capture after the boy reappeared, unharmed and with no recollection of the abduction. They meet Tobias Rice, another meteor freak with the ability of identifying the meteor-infected. After Chloe herself disappeared for a day, in which she was subjected to invasive experimentation, she realized that she was targeted because someone identified her as a meteor freak. She told Clark that she was afraid that she might have powers that will manifest and make her a danger to herself or others. Clark promised he will be there to help her control her powers, if she ever developed any.
On her wedding day, Lana locked Chloe in the wine cellar of the Luthor Mansion, knowing she'd call Clark for help. She watched as Clark used his abilities to free Chloe, and listened as Chloe told Clark that he needed to tell Lana the truth and save her from a loveless marriage. Nevertheless, she still supported Lana and performed all of her Maid of Honor duties.
When Lex obtained a drug that brought Chloe's mother, Moira Sullivan out of her catatonic state and used her to control other metahumans, Moira controlled Chloe first and tried to use her to escape. Chloe was captured and sent to the 33.1 facility, but she and her mother were saved by Clark. However, the drug wore off and Moira slipped back into catatonia. With Oliver's help, Clark and Chloe transferred her to a safer facility. Chloe started writing an article about LuthorCorp's projects until Lex came by and threatened her if she published the story.
Chloe's resentment towards Lex continued to grow and she refused to help when he was trapped under the rubble of a series of tunnels. However, after Clark also gets caught in the same place, she began looking for a way out and finally succeeded with the help of Lana. Also because of this, Chloe began to notice that Lana had begun to feel a great hatred towards Lex and started to worry about her friend. After Lana was shot, she admitted to Chloe that she had only married Lex to protect Clark.
Jimmy was sent on an assignment in Milwaukee by the Daily Planet, which meant leaving Chloe. However, they didn't break up, but parted on optimistic terms.
Despite her cousin warnings, Lois investigated Lex projects and ended up getting stabbed in the stomach at Reeves Dam. She called Chloe, who arrived to find Lois bleeding to death. As Chloe wept over Lois' body, her dormant meteor power manifested itself and Lois was instantly healed, leaving Chloe unconscious.
In Season Seven... After Chloe healed her, Lois woke up and found her cousin unconscious. She takes Chloe to the hospital but it was too late, and Chloe was pronounced dead. However, she inexplicably regained consciousness in the morgue. Clark helped her escape, and they both learned of Lana's death. Chloe helped Clark defeat Bizarro, and they both mourned for Lana. However, they soon discovered that Lana had faked her death in an attempt to escape from Lex.
When Chloe returned to work at the Daily Planet her first meeting with the new editor, Grant Gabriel, proved disastrous when he proclaimed her a washout. When Lois showed Grant her story about a spaceship she found in the woods, he gave her a job with a desk right next to her shocked cousin. This ship turned out to belong to Clark's Kryptonian cousin, Kara, who Clark brought to the Daily Planet to meet Chloe.
After some weeks, Jimmy returned to town and was eager to spend time with Chloe, but she was preoccupied with anxiety over her meteor-rock infection and pressure from Grant Gabriel. Jimmy offered to start hunting stories about metahumans to re-launch her career, but Chloe refused the idea and asked him to please stop calling the infected people “freaks”. Due to Chloe's distance and unexplained mood changes, she and Jimmy began to grow apart. Jimmy formed a friendship with Kara, and he and a jealous Chloe argued about his connection with her.
When Chloe found out that a doctor performed a procedure to cure meteor-rock infection, she was willing to risk six years of memory loss to have it done. However the doctor turned out to be a serial killer who targeted the meteor-infected. Clark saved her and she returned to Jimmy, wanting to start over in their relationship. Jimmy asked if their relationship could be “normal”, but when Chloe couldn't promise him this or tell him her concerns, he broke up with her.
As she started to accept her condition, Chloe began to seek for emotional support and found The Isis Foundation website. She went to the Foundation to find out more and was quite surprised to discover that it was owned by none other than Lana. Lana explained the conditions under which she had decided to found the institute and asked Chloe to keep it secret from Clark. Chloe agreed, even though she was worried about her friend's behavior.
When Adrian Cross used Chloe as leverage to make Lois expose Lex's illegal cloning project, he planted a bomb on Chloe and trapped her in an elevator with Jimmy. Convinced she was going to die, she confessed her meteor infection to him. However, Bizarro, posing as Clark, saved the two because he needed her to decipher a Kryptonian message. Chloe later displayed her power to Jimmy, showing that she had gained control over them.
When “Clark” started to forget things and act strangely, Chloe asked Lana if she'd noticed. Lana thought Clark had just changed his priorities and they announced they were leaving Smallville forever; Chloe was extremely upset. She soon discovered that the Clark that had been living with Lana was really Bizarro, and she stole the Kryptonian shield from the farm. When the real Clark returned, Chloe made him prove he was himself before she gave it to him.
After all the troubles caused by Bizarro, Clark avoided his issues with Lana by visiting Chloe at work. After Chloe was attacked by Black Canary, Clark realized that she had been helping Oliver with his missions. Although Clark was angry that Oliver had put her in danger, Chloe told him that the work was exciting and she enjoyed doing it.
When Clark entered Lex's subconscious and almost died with him, Chloe used her healing ability to save Lex and allow Clark to regain consciousness. But using her power killed her for eighteen hours. Clark watched over her until she awoke and asked her not to use her powers again. Chloe was confident in her decision, and wondered why she had been given such an amazing gift out of all the meteor abilities so far seen. But they both wondered if she'd ever “die” permanently.
When Clark was kidnapped, Lana and Chloe suspected Lionel after discovering a kryptonite dart, but he tried to convince them that Lex was responsible. Chloe saw through Lionel's lies and found Clark's location. She took Kara, who had total amnesia, to the Fortress and pleaded with Jor-El to restore Kara's memories. He did and Clark was rescued, thanks to Chloe.
After Brainiac resurfaced, Chloe helped Clark track his location. She eventually located him at the Isis Foundation, but they were too late to stop him from attacking Lana, leaving her catatonic.
Lionel Luthor approached Chloe and asked her to tell Clark to listen to him, but Chloe refused, not trusting him after all he had done in the past. After Lionel committed apparent suicide, Chloe discovered that he had left his Veritas key in her desk. When Lex discovered it hidden there he fired Chloe, and she suspected that he had actually murdered his father.
As Chloe and Jimmy rekindled their relationship, Jimmy continued to display the same insecurities and was upset that Chloe seemingly blew him off under the excuse of managing the Isis Foundation in Lana’s absence. When Chloe devised a plan to hack into the Metropolis Satellite Center, Jimmy was approached by Vanessa Webber, an agent of the Department of Domestic Security who convinced him that Chloe was part of a terrorist sleeper cell. Vanessa forced him to spy on Chloe, but he double-crossed her. Unbeknownst to Chloe, it was actually Lex that prevented her from being arrested, and Lex continued to blackmail Jimmy with Chloe's freedom.
After Clark became so depressed that he wondered if the world would be better off if he'd never came to earth, Chloe tried to cheer him up and watched horrified as Clark was transported to such an alternate reality. When Clark returned, Chloe assured him that the world needed him, and he was able to go back to Krypton, stop Brainiac, and bring Kara home.
Chloe and Clark start to investigate Veritas and track down its last living member, Edward Teague. When Teague attempted to kill Clark, it was Chloe who arrived just in time to save him. Teague was later killed by Kara, much to Clark and Chloe's shock. During a meeting with Kara, Chloe realized that “Kara” was actually Brainiac, just before he attacked her. However, Chloe's meteor power protected her from being completely controlled and significantly weakened Brainiac. Chloe was rushed to the hospital and kept in intensive care until Clark was able to defeat Brainaic for good.
Chloe recovered fully and Jimmy took her home. Jimmy asked Chloe to marry him, because he realized that he never wanted to lose her, but before Chloe could answer, she was suddenly arrested for terrorism by agents claiming to be from the DDS.
In Season Eight... Four weeks after her arrest, Chloe was in the custody of who she thought was the Department of Domestic Security and was forced to use her new ability of processing information at superhuman speed to decipher encoded telephone numbers of suspected terrorists. But when she realized that she was really working for LuthorCorp, she tried to escape but failed. She was rescued by the Justice League but in the process Clark was seriously injured and when Chloe tried to heal him found her healing powers were inactive. Upon returning home, Chloe accepted Jimmy's marriage proposal.
Chloe reopened the Isis Foundation and told her friends that she was engaged. While she helped a victim of an explosion that occurred outside the Daily Planet, she struck up a friendship with a paramedic on the scene, Davis Bloome. When Oliver was poisoned, Chloe called her new friend to treat him and used her new ability to research a cure, leaving Clark worried about the effects of her new power.
Jimmy moved in with Chloe and discovered the love letter that she had written for Clark when he was sick, and questioned her love for him. They discussed the letter and she told him that she no longer has those feelings for Clark. She asked Clark to give her away at the altar.
When she and Jimmy held an engagement party, they were kidnapped by a jeweler, who tortured the couple by forcing them to reveal their true feelings and Chloe revealed that she was not in love with anyone else other than Jimmy.
Her friendship with Davis continued to grow and when a member of the group sessions that Chloe moderated at the Isis Foundation was murdered, Davis confessed to her that he could be the murderer. She refused to believe this and felt drawn to prove Davis' innocence. He questioned her motives for helping him, and insinuated that she might want more than friendship with him, but then Chloe told him she that wasn't the case and that they should distance themselves from each other for a while.
When Chloe realized a metahuman named Sebastian Kane that had been sent by Tess Mercer knew about Clark's secret, she visited him at the hospital and used her new ability to overload his brain with information, killing him.
When Clark and Lois were transported to the Phantom Zone, Chloe deduced that it had something to do with Clark's Crystal of Knowledge, and recruited Oliver’s help to steal a generator from Tess so she could use it to rescue them. Using her abilities, she “hacked” into the crystal and created portal through which her friends could return. However using her abilities once again proved risky to her health.
Chloe began to have significant bouts of memory loss and deduced that Brainiac was slowly taking over. When she could only remember Davis, Clark rebuilt the Fortress of Solitude and took Chloe there, where Jor-El agreed to restore Chloe by removing the Brainiac infection, but also Clark asked him to erase all the memories Chloe had about his secret. Without the burden of Clark's secret, Chloe was happy in her life, and thrilled to be marrying Jimmy. But then Davis approached her and told her that he did not want to watch her marry the wrong man, and kissed her.
On the day of her wedding, Chloe kept receiving desperate calls from Davis, but chose to ignore them. After the wedding, at the reception, a creature attacked and injured many people, Jimmy most seriously. The creature addressed Chloe by name and kidnapped her and took her to the Fortress of Solitude. The Fortress had been taken over by Brainiac, and he possessed Chloe and used her as his vessel.
Brainiac took full control of Chloe's body and revealed his plan to destroy the earth while draining all humans of their knowledge. With the help of the Legion of Super-Heroes from the future, Clark extracted Brainiac from Chloe. She completely recovered, with her memory almost completely restored, including the knowledge of Clark's secret. However, she said that she does not clearly remember the time leading up to the wedding. She told Clark that next time he should do the right thing for the world, and not for her.
Chloe went periodically to Star City to care for her husband as he recovered, and at same time helped Clark go undercover to find out who shot John Jones. After Oliver was nearly killed by an explosion in LuthorCorp, he asked Chloe to secretly track down Winslow Schott. Although Chloe helped Oliver, she did not agree with his murderous vendetta, especially after learning that he killed Lex Luthor. But Oliver revealed that he knew that she was responsible for the death of Sebastian Kane. Chloe denied responsibility, saying it was Brainiac's actions, but Oliver wondered if she could have been driven by her instinct to protect Clark.
Jimmy was transferred to Metropolis General, but suffered from extreme pain and nightmares about the wedding. Chloe suggested he talk to a psychologist, but Jimmy refused. After seeing Davis kill a man in the hospital, Jimmy became extremely paranoid. Chloe and Davis tell Jimmy it was just a hallucination, caused by his medication, but Jimmy doesn't believe them. He started investigating Davis, but even though he found out that Davis really had killed the man, he also started having actual hallucinations, so Chloe didn't believe him. And when Jimmy violently confronted Davis, Chloe had to taser him to keep him from hurting Davis. Because she chose Davis over him, Jimmy told Chloe that marrying her was the biggest mistake of his life, and leaves her heartbroken.
With her life a mess, Chloe went through an identity crisis and confessed to Oliver at her birthday party that she was jealous of Clark and Lois' journalism partnership. After being turned into Lois by a magician at the party and living as Lois for a day, Chloe realized what she wanted to do with her life and officially joined Oliver's hero team as Watchtower.
Chloe started to spend more time with Davis since she found him a sympathetic ear, but Clark thought she was trusting him too much. He was proved right when they discovered that Davis was the serial killer that had been killing people in the city. Davis confronted Chloe, confessing that he was the one who destroyed her wedding, was the one sent to kill Clark, and asked her to help him to die. Tearfully, Chloe bathed Davis in liquid kryptonite, against Clark’s desires. However, Davis reemerged later stronger than ever and hid in the basement of the Talon. When Chloe found Davis, he told her that she was the only one who stopped him from mutating into the beast and asked her to stay with him.
Chloe began harboring Davis without anyone's knowledge but soon the situation started to become more unbearable as Davis started to kill to protect her. She almost confessed her situation to Lois but didn't. Later when Clark asked her why she was being so distant, Chloe claimed that she was just under a lot of stress.
Chloe asked Dr. Emil to try to find a cure for Davis, but he told her that there was nothing he could do. Davis became increasingly needy towards her, saying that he could not be physically apart from her anymore. Clark took Davis to the Fortress, planning on sending him to the Phantom Zone, but Chloe stopped him, believing that it was not the best solution. As a last resort, she left town with Davis and later phoned Clark to tell him to not look for her. Clark insisted that she was doing the wrong thing but Chloe believed she was sacrificing herself to keep Clark safe.
Some weeks later, Chloe and Davis were finally captured by Oliver's team and after a brief argument with Oliver about how to deal with Davis, Chloe separated Doomsday from Davis using black kryptonite. She and Davis waited with Jimmy at a loft apartment, called the Watchtower, that Jimmy had purchased for them, and as Jimmy explained that he had learned Clark's secret, Chloe told him she was only with Davis to protect Clark. Hearing this, Davis flew into a rage and attacked them, mortally wounding Jimmy and attempting to kill Chloe. Jimmy was able to kill Davis before dying in Chloe's arms. With his last breath Jimmy told Chloe that he loved her.
Chloe later reunited with Clark at the Watchtower, where he tells her that Lois has disappeared and he can't find her anywhere. Then, consumed by the mistakes he had made, Clark told her that his human persona was hindering his destiny as a hero. He told Chloe that “Clark Kent is dead” before departing, leaving Chloe alone and completely heartbroken.
In Season Nine... Without any signs of Clark, Lois, or Oliver, Chloe took refuge in the Watchtower and spent her time trying to find her friends. When Lois suddenly reappeared, Chloe visited her in hospital and learned that she has been in the future and that had not come back alone. After Dr. Emil Hamilton filled the loft with computers so she can work better in her projects, Chloe finally contacted Clark and warned him to watch out for the assassin that had followed Lois from the future. Chloe pleaded with Clark to use the Legion ring to go back in time and save Jimmy, but Clark flatly refused. Chloe became very angry, reminding him how much she had sacrificed for him. Distraught, Chloe left Clark, ending their friendship.
After Chloe discovered that Lois had been receiving calls from the Blur she confronted Clark and warned him to stop contacting her cousin. Eventually, Clark apologized to Chloe for leaving her and Chloe encouraged him to return to his life as Clark Kent.
Using the resources of her new Watchtower, Chloe and Emil used Clark's Kryptonian blood to create an antidote when a mutant-zombie virus struck Metropolis. During this time, Emil revealed that he knew that Chloe had been using the resources of the Watchtower to spy on Oliver and the rest of the team, but she assured him that was the only way to keep them safe.
When Oliver got into trouble with a woman at a casino and called on Chloe for help, he worked out that Chloe had hired the woman in order to force him over the edge and face his demons. Initially he was disapproving of Chloe's methods; he thought she had put their friends in danger. But after she reassured him that everyone was kept safe, he became grateful. He thanked her sincerely, telling her “You saved my life, Chloe. Both the myth... and the man.”
Chloe continued to help Clark, using the resources of the Watchtower. She helped him track and research the Kandorians, as well as investigate Tess' involvement with them and the extent of her knowledge about Clark. Chloe also watched and Clark and Lois grew closer, and when Clark told Chloe how he felt about Lois she admitted to him that she already knew how they felt about each other, and that she believed they were destined to be together.
When Lois was attacked by a mysterious assassin, Chloe investigated but soon found herself the victim of the attacker. She managed to escape with only a wound on her arm. She believed that Oliver was the one who attacked her and Lois, and she told Clark about what she had done to bring back Oliver from the dark side. Oliver later turned out to be innocent, and ended up stopping the attacker. Clark then became worried that she spending too much time in the Watchtower, seeing people through her screens too much. He told her that she go out into the real world more, but she claimed that she was fine.
Chloe was found by Sylvester Pemberton, who knew her Watchtower identity and those of her fellow superheroes. Before he could ask for her help, Sylvester was killed by Icicle. She and Clark later investigated the murders of other victims that Sylvester was connected to, learning about the Justice Society of America. Chloe, Clark, Oliver, and John Jones joined forces with Hawkman, Stargirl, and Doctor Fate to stop Icicle from killing them.
During her time spent with the JSA, Chloe learned that she and others are more than just a team, they're a family. Stargirl advised Chloe to make the Watchtower feel more like a home, and that she and the other heroes should get together on occasions that don't involve missions. John also warned Chloe that she could lose herself by isolating herself from the world and only seeing people through cameras.
Chloe took her friends' advice, and started going out into the real world more. She also grew much closer to Oliver. One night at the Watchtower, they bonded over how neither of them seemed to have fun, and later shared their first kiss as Oliver taught her how to shoot an arrow.
As Chloe and Oliver became an item, Oliver confronted Chloe about taking money from his company. Chloe explained what she had done by showing Oliver her arsenal of kryptonite weapons. Chloe felt that, since Clark seemed incapable of standing against Zod and the Kandorians and was determined to make peace, she could no longer sit back and just trust him to work it out.
Chloe and Oliver decided to have a secret weekend getaway in a B&B, and end up bumping into Clark and Lois. After the awkward moment between the couples, Lois talked to Chloe about her relationship with Oliver. Chloe claims that they are not a couple, just having fun together without any strings, but Lois told her that she is glad to see them together. Oliver bought a gift for Chloe, but she turns it down, saying that she wouldn't want their relationship to become complicated. Later, Chloe begins to open Oliver's gift but hesitates. She and Oliver then talk about their relationship, deciding to put their past relationships behind them and move on together, and their relationship becomes more serious.
When Clark became infected with red kryptonite again, Clark turned on Chloe after she confessed to him about her kryptonite arsenal. Chloe then had to rely on Tess to stop Clark from joining Zod and revealing all of his secrets. Once Clark was cured, Clark and Chloe reconciled. She understood what Clark was going through, and that Clark felt jealous of what Chloe and Lois shared as a family.
When Tess broke into Watchtower, the building triggered its security system, trapping Chloe and Tess inside. They began to work out their differences and realized Checkmate was their common enemy. Tess says that Chloe hides herself behind the computers and Chloe admits that she's had problems believing in people again. Once Chloe realized Tess was being monitored by Checkmate, they devised a way to escape, although this resulted in the destruction of Watchtower. Once they escaped, Chloe helped disarm Tess' GPS tracker but the only way to do this was to kill her. Chloe considered not reviving Tess, but she ultimately does, saying she promised Tess she would and that now Tess owed her.
Chloe continued to help Clark find the Book of Rao in the remains of her Watchtower, but kept coming across blocks by the mysterious Red Queen. Chloe eventually came to learn that the Red Queen was actually Martha Kent, who was using her power as a senator to help protect Clark's secret.
When Clark came to her, asking her to restore Watchtower, she apologized for everything she had done, saying that it was all to protect him. She told him she wasn't ready to be Watchtower again, and that she wasn't a hero like him. With Oliver in her life, she just wanted to live in the real world again. But after an uplifting pep-talk from Clark, she agreed to become Watchtower once again.
When Clark decided to leave Earth and take the Kandorians to another world, where they could live in peace and rebuild their society, Chloe was deeply saddened. However, she supported his decision, believing that Clark could become a great leader to his people. She told Clark she was very proud of him, and she and the other members of the League promised to watch over the Earth in Clark's absence.
Later, Oliver tells Chloe that he had a satellite launched specifically for Watchtower, and also as a gift to her, but that the satellite needed to be brought online manually at another location. They start the mission, and after Oliver gets the link up, he is attacked as Chloe listens helplessly from the Watchtower. Oliver confesses his love for her, and she tells him she loves him too. Just before the line cuts off, he tells Chloe that his attackers were not the Kandorians.
In Season Ten... After watching a video of Oliver's abduction, Chloe exhausted all her resources to try to find him. She eventually resorted to using the Helmet of Nabu, which showed her some of the future and how to help Oliver, and left her unconscious. Once she recovered, she relayed part of what she had seen to Clark and sent him on a mission to stop Lex's clone. After he left, Chloe sadly said goodbye to him, and later traded herself for Oliver in order to save him.
When Chloe left, all the records of her existence disappeared, making it appear as if she had never been born. Tess revealed to Oliver that Chloe had asked for her help resetting the Watchtower computers so no one could find her. Later, Oliver learned that rather than suffer further torture, Chloe had killed herself with a cyanide pill to protect Oliver from Rick Flag. However, Clark and Oliver came to the conclusion that she had faked her own death after finding a cyanide antidote in her apartment. Clark determined that after seeing the future, Chloe had planned her departure for unknown reasons.
Although Chloe was gone, with no sign of when or if she would return, Oliver remained faithful to her.
Despite falling off the grid, she still contacted the new editors of the Smallville Torch newspaper the night after the high school reunion, pleased that they had been continuing her work with the Wall of Weird, which they formatted digitally. Her message thanked them for “carrying” her Torch. Also, it was revealed that she had become a legend in the Smallville High due to her stories about the bizarre and rare things that she investigated.
After Lois and Clark get engaged, Chloe sent Lois a letter with a gift for her wedding day, congratulating her. A flashback revealed that before her disappearance, Chloe talked with Lois about why Clark and Lana's relationship never worked out. When Lois questioned Chloe about her relationship with Oliver, Chloe instantly understood that Lois had discovered Clark's secret and then encouraged her cousin by saying that Lana was never destined to be with Clark. Apparently, Chloe had seen Lois' future, as she was the first to congratulate Lois on her engagement almost immediately after it happened.
After months of being missing, Chloe reappeared and used the resources of the Suicide Squad to save her friends after they were abducted by the VRA. Although Clark felt as if he couldn't trust her after her unexplained disappearance, he eventually gave Chloe another chance, thanks to Lois' influence. Chloe talked to Clark, and later Oliver, and explained that after putting on the Helmet of Nabu, she saw that her friends would be kidnapped and decided to leave in order to save them at the right moment. Lois asked Chloe to be her Maid of Honor, which Chloe joyfully accepted. Later, at the Watchtower, she told Oliver that she planned to stay in Metropolis, and they reunited with a kiss.
When the VRA was officially rejected, Chloe and Oliver decided to go out on an anniversary date at the Ace of Clubs. Since they had trouble going out under their true identities, they used another couple's surname to get an already reserved table. Chloe and Oliver then became embroiled in a mystery involving the Darkness, which ended in Chloe being kidnapped by Desaad. She was confronted with hallucinations of the Deadly Sins and unfulfilled dreams, but bravely resisted. After being rescued by Clark, Chloe revealed to Oliver that she regretted erasing her identity and felt lost; especially when she looked back on the person she was in high school.
After getting magically drunk at Lois and Clark's engagement party, Chloe found half of a marriage certificate with her name on it and mistakenly thought that she had married Clark. She eventually found out that their drunken wedding was just a prank, and she met Clark at the barn and told him so. She also informed him that she was officially retiring from being Watchtower, and was once again leaving Metropolis because she had discovered what she wanted to do with her life: return to journalism, and find more heroes and inspire them to reach their full potential. She said she was moving to Star City, and after one last reunion with the group in the Watchtower, Chloe snuck away to leave. She was stopped by Oliver, who revealed that it was in fact him that she married the night before. Chloe and Oliver left for Star City together, to start a new life and husband and wife. They get an apartment together, mixing her geek chic and Oliver's hero green predilection.
Chloe returned to Smallville for Lois and Clark's wedding. She was concerned when she realized that Lois had decided not to marry Clark, so she meets with her cousin and gives her a copy of Clark's vows. After reading them, Lois realized that she and Clark were truly meant to be together and decided to go through with the wedding.
At the wedding, Chloe happily watched as her cousin and her best friend walked together down the aisle. During the ceremony, the ring that Oliver had shown her earlier drew Chloe's attention because something about it was different. She began to sense that something was not right. Chloe noticed that the ring grew brighter as it approached Clark's finger, which she then realized it was made of gold kryptonite. Chloe quickly intercepted the ring before Lois could put it on Clark, and watched in horror as Oliver revealed he was possessed by the darkness. With Lois' help, Chloe drove everyone outside the chapel as a battle between Clark and a possessed Oliver began.
After Clark managed to save Oliver, Chloe met with them at the Kent Farm to begin investigating the coming Apokolips. With the Watchtower systems out of service, Chloe told her friends she needed to return to Star City to use her equipment and database to investigate more and call the other team members; taking up her position on the team as Watchtower once again. She gave Clark a hug and left him, saying “See you in the funny pages.”
Oliver asked Chloe to let him accompany her to Star City, but she refused, telling him that he needed to stay and do what he does best, “Be a hero.” Oliver smiled at her and replied “You too, Sullivan” and kissed her goodbye.
A hero in her own right, Chloe left for Star City.
Seven years later, Chloe reads a comic book to her and Oliver's young son. The story is about an amazing boy from Smallville, who grew up to become the world's greatest hero, Superman...
Partial credit for this biography goes to the amazing Smallville Wiki.