When Clark's cousin Kara arrives on the scene, Clark advises her to keep a low profile and master her powers, but Kara has other ideas and becomes the focus of Lex Luthor's powerlust. And, there are two Clark Kents: one is the young man whose life in a tiny Kansas town sets him on destiny's path. The other is a Bizarro who shares Clark's DNA, but not his values. Lane makes a career leap and Chloe Sullivan finds that balancing a meteor power with a personal life isn't easy.
Lex is rescued from a watery death by a mysterious woman and must face justice for Lana's murder. Chloe's fate is revealed. Clark battles the last Phantom Zone wraith, who has all of Clark's abilities, and struggles to come to grips with all of the day's occurrences that have affected his loved ones and his destiny.
Clark and Lois meet Smallville's newest arrival face-to-face, and she has some surprising news. Clark decides to leave Smallville and continue with his superhero training but Jor-el informs him that a new Kryptonian menace has arisen.
Kara takes to life in Smallville by getting a job at the Talon, and entering the Miss Sweet Corn Pageant as a contestant, overruling Clark's objections. However, Lex takes an interest in her and three of the other contestants discover she has super-powers and decide to use her to steal a valuable time capsule.
Dr. Curtis Knox says he can "cure" someone from being a "meteor freak," changing their lives. Chloe takes an interest in this, but Dr. Knox may have another secret.
[Dr. Knox seems to be Vandal Savage, an 25.000 years old immortal. There are several references to his past and there is the antique watch, a symbol of Vandal Savage]
When a movie is shot in Smallville, Clark is forced to secretly use his powers to save someone from a runaway car... but somebody is looking and becomes Clark's biggest fan. Meanwhile, Lionel's fate is revealed.
Kara goes to Washington to look for her missing crystal, but is captured after she breaks into the lab. She's sedated with a truth serum that has kryptonite in it, which makes her relive a trip to Earth from the past. In this past trip she followed Lara, Clark's biological mother, to the Kent's farm. Clark saves Kara, but also ends up being affected by the serum when he burns it with his heat vision.
Lana absorbs Clark's powers during a lightning storm, which she uses to break into Lex's safe and steal some incriminating evidence. After being turned away by Grant at the Daily Planet, who won't accept her stolen evidence, Lana goes after Lex herself. Clark tries to rescue Lex, but must first battle the super-powered Lana.
Clark hears his mother's voice trapped in Kara's crystal, and releases her. She gives him Jor-El's ring made of Blue Kryptonite, which strips him of his powers.
A mysterious man who claims to be a product of Lex's latest project plants a bomb on Chloe and uses her to force Lois to get the truth from Lex.
Chloe begins to notice that Clark's not acting like himself. Bizarro enlists the help of Brainiac.
When Green Arrow's band of heroes thwarts his efforts once too often, Lex employs a super-powered vigilante to take down the Emerald Archer.
Lex tracks the amnesiac Kara to Detroit, where Lois follows him. An obsessive busboy infatuated with Kara shoots Lex, and Chloe has to determine whether to heal him or not.
Pete Ross returns to town and finds a number of surprising changes since his departure. Besides resolving his feelings toward Clark since he learned of his friend's secret, Pete has to deal with the acquisition of a superpower of his own.
Lionel has Clark kidnapped, and when Chloe and Lana confront him, he makes them think Lex is the culprit. Chloe and Lana then beg Jor-El to restore Kara's memory because she's the only person who can rescue Clark.
Clark must learn a new superpower as he and Kara join forces to take on Brainiac, putting the lives of their friends in danger.
No one is safe when Lex seeks the secret of Veritas, and Clark tries to stop him.
While Clark seeks out Brainiac to force him to fulfill his side of their bargain and restore Lana, Chloe and Jimmy go up against the government.
When Clark wonders if the world would be better off if he never came to Smallville, Jor-El shows him what life would have been like if he had never existed.
After Lex is attacked by a mysterious stranger, he and Clark both discover the last surviving member of the Veritas group who holds the secret to controlling the Traveler.