As the seventh season begins, Clark faces his most deadly enemy---his Bizarro doppelganger---after Lex's secret lab at Reeves Dam is destroyed; Lex is saved from drowning by a mysterious female savior, but his past catches up with him.

Clark meets his cousin Kara, but decides that there is nothing for him in Smallville without Lana, so he heads to the Fortress of Solitude to begin training as a superhero. Once there, Jor-El tells him Kara's father is evil and she is dangerous, so Clark must return to Smallville.

Clark hopes Kara will keep a low profile, but three meteor-infected girls want to use her as part of their scheme after one of them sees Kara's special powers.

Chloe learns that a doctor, Dr. Curtis Knox, has been treating meteor-infected people and removing their abilities. Desperate to get rid of her powers, Chloe makes an appointment to see him, unaware that Dr. Knox has a nefarious plan to kill his patients and harvest their organs. Meanwhile, Kara cons Jimmy into helping her locate her crystal and defies Clark's order to stay on the farm after she discovers its whereabouts. Lana sets up secret surveillance of Lex.

The residents of Smallville are thrilled when Warrior Angel, a movie based on a comic book, begins shooting in town. However, after the lead actress, Rachel Davenport takes off in stunt car with cut brakes, Clark must step in to stop the runaway car. Unfortunately, an obsessed fan witnesses this heroic event and decides Clark is a real life superhero, whose girlfriend Lana must be eliminated so Clark can fulfill his destiny. Meanwhile, Lex discovers Lionel at the cabin.

Clark learns Kara is in Washington searching for the crystal. Kara is captured after she breaks into the lab and sedated with a kryptonite-infused truth serum. The serum causes her to relive a prior trip to Earth when she followed Clark's biological mother, Lara, to the Kent farm. Clark arrives in time to save her but, after searing the machine with heat vision, he also falls victim to the serum and sees what Kara sees: his mother.

Kryptonite and high voltage mix during a lightning storm, causing Lana to absorb Clarks powers. Using her newfound super powers, she breaks into Lex's safe and steals incriminating evidence which she then delivers to Lois and Grant, demanding they run a story exposing Lex's secrets. After Grant refuses to use stolen material, Lana decides to take care of Lex herself. Clark tries to stop Lana from killing Lex and a super battle ensues between the two.

Clark hears the voice of his biological mother, Lara, calling for help from Kara's crystal and decides to release her, despite Jor-El's warnings. Lara and Clark reunite and she gives him Jor-El's ring, which contains blue kryptonite. As Clark puts it on, he realizes Zor-El manipulated the whole thing and that blue kryptonite strips him of his powers, enabling Zor-El to take control of the Fortress of Solitude. Meanwhile, Chloe and Lex each discover Lois and Grant have been seeing each other and warn them to stop.

Clark returns to Smallville from the Fortress and tells Lana that Kara is gone. Clark tells Lana they should team up to being Lex down, so she gives him all the information she's gathered so far. Adrian secretly plants a bomb on Chloe and tells Lois if she doesn't get Lex to admit the truth about his experiments with cloning, he will detonate the bomb. Chloe, thinking she is about to die, confesses to Jimmy that she is a meteor freak.

Bizarro adopts to his new life with Lana, pretending to be Clark. Meanwhile, the real Clark remains frozen in the Arctic thanks to the Jor-El programming. However, Bizarro needs the help of Brainiac to stabilize his form and the two make a deal. Meanwhile, Grant goes to Lionel and reveals his true identity, much to Lex's anger.

Chloe, working with Oliver Queen, intercepts one of Lex's files but is attacked by the Black Canary, a vigilante who takes the info from her. The woman returns the info to Lex, who asks her to take out the vigilante that has been attacking his operations: Green Arrow.

Lex finds Kara in Detroit working as a waitress and offers to restore her memories, only to be shot in the head by an obsessive busboy. Clark must use experimental LuthorCorp technology to enter Lex's memories and find out where Kara is, while Chloe contemplates whether to use her powers to heal Lex, despite the risk to herself.

Pete is working as a roadie for OneRepublic and develops super-stretching powers after chewing kryptonite-tainted gum. He ends up rescuing Kara and decides to go public with Jimmy's help. However, Lex puts pressure on him to steal Kara's bracelet from Lionel, by threatening to reveal Chloe is a meteor freak.

Clark is abducted and held in a kryptonite-lined cell at an abandoned hanger. After Chloe and Lana find a military electric probe at the farm, they confront Lionel, who suggests Lex may be responsible. Chloe and Lana get Kara away from Lex and get her to the Fortress, hoping Jor-El can restore her memories. Meanwhile, the daughter of Dr. Swann meets with Lex to discover his father's involvement with the Veritas group.

Brainiac seeks out Kara to convince her to come with him, and when she refuses he strikes at someone close to Clark. Meanwhile, Lex attempts to get the information on Veritas that Lionel has hidden away, and begins to remember what really happened on the day of the meteor shower.

Lex seeks the key in Lionel's locket so that he can uncover the secret of Veritas that will give him control of the Traveler. In his quest, he takes the last final step to evil by killing someone close to Clark.

While Clark tries to find Brainiac and Kara, Chloe inadvertently draws the government's attention with her computer searches. A NSA agent forces Jimmy to spy on his girlfriend and determine if she's working for a terrorist cell as they suspect. Meanwhile, Lex recovers the box in Zurich and discovers there are people who will kill to keep him from obtaining its secrets.

Clark has discovered that Brainiac plans to destroy him as a baby, but believes the world would be better off without him and refuses to go back to save himself. He then finds himself swept into an existence where he never existed, and discovers what happens to an Earth without him.

While Lex considers the ramifications of his discovery in the deposit box in Zurich, Jimmy researches the symbols in the Kawatche caves, while Clark investigates a mysterious symbol that leads him to the last surviving Veritas member.

Kara tells Lex he is destined to defeat the Traveler and offers to take him to the Fortress to learn how. Clark is stunned that Kara would go to Lex but it is revealed that Brainiac is impersonating Kara and she's actually trapped in the Phantom Zone. Chloe is arrested by the Department of Domestic Security and Lana awakens from her comatose state. Meanwhile, in an epic turn of events, Clark and Lex face off in the Fortress and Lex learns Clark's secret.