Clark must save Pete from literally being devoured by a female classmate whose crash diet of kryptonite-infected vegetables causes her to shed weight faster than she can handle and must somehow satisfy her ravenous hunger. Meanwhile, Lex gets one step closer to the truth about Clark after funding a study on the green meteor fragments.

Clark and Lex team up to rescue Clark's high school class after a janitor takes them hostage in LuthorCorp. He claims his deadly "jitters" were caused by a mysterious contaminant and threatens to kill everyone unless he is shown a secret sublevel - which Lionel Luthor denies ever existed.

Clark's secret identity is at stake when a bad cop witnesses him use his superhuman powers and coerces Clark to join forces with him; however, when Clark double-crosses the cop, he is not prepared to deal with the consequences for him and his family. Meanwhile, Lex receives an intriguing proposal from an old British flame.

A teen girl's obsession with Lex turns life-threatening when invisible attacks in Luthor Mansion pits Clark against an undetectable enemy. Meanwhile, Clark is thrilled when Lana looks to him for companionship after Whitney inexplicably pushes her away.

Clark is stunned when a pesticide magnate who has kryptonite-enhanced powers of persuasion somehow convinces Jonathan to sell the family farm to make way for a new plant. Clark teams up with the local hermit whose mysterious past holds the key to the town's future.

When Clark rescues his classmate Eric from harm during an electrical storm, they are both struck by lightening, resulting in all of Clark's superpowers transferring to Eric. While Eric relishes his new life as "Superboy," Clark is torn between his happiness at finally being normal and his growing concern for the town's safety as Eric starts to abuse his powers. Meanwhile, Lex believes he finally has undeniable proof of Clark's superpowers and confronts him.

Clark and Lex are stumped when the Luthor mansion is robbed by burglars who seem to have the ability to walk through walls. Lex's curiosity turns to desperation when he discovers the thieves have stolen evidence of his secret project and Clark wonders if his dad was right about Lex's deceit all along.

Lex faces the consequences of his shady dealings in Metropolis years ago when an old enemy comes to Smallville intent on destroying his life, ultimately putting Clark and Lana in harm's way. Meanwhile, Clark has his hands full as he tries not only to protect Lex from the past, but also keep Chloe out of his after she discovers a mystery surrounding his adoption.

Clark must solve the riddle of the mysterious Nicodemus flower and Lex's shady involvement after it infects the residents of Smallville removing their inhibitions - Jonathan becomes a couch potato, Lana puts the moves on Clark as the town Lolita and Pete tries to kill Lex - then puts them into a deadly coma.

After Martha accidentally hits a young boy with her car, the Kents take him in until they can locate his parents, unaware that the boy can read minds and has unlocked the secret thoughts of Lex, Lana, Jonathan and Martha, which puts Clark's secret in jeopardy. Meanwhile, Lex must decide if he wants to take his father up on his job offer and move back to his old life in Metropolis.

Clark must stop a kryptonite-infected man who seeks to relieve the suffering of the elderly and sick by turning them into ashes - and Whitney's ailing father may be his next victim. Meanwhile, Lex is furious after his father sends someone to look into LuthorCorp's financial records and this man reveals Lex's secret investigation into Clark and his family.

Clark sees the election for class president as an opportunity to be a "normal kid," but when his running mates are systematically attacked by a swarm of bees, Clark suspects a candidate is eliminating the competition one by one and he is next on the list.

Clark faces an unexpected foe when a gifted art student returns to school after a hit-and-run accident robbed him of the use of his hands but gave him the gift of telekinesis, and he is seeking revenge against those he holds responsible. Meanwhile, Lana becomes jealous after watching Clark with Chloe and begins to question her relationship with Whitney.

Clark and Lana race against time to find a kidnapped Chloe after a kryptonite explosion gives Lana the ability to "see" through the kidnapper's eyes and she watches Chloe being buried alive. Meanwhile, Lex discovers evidence that a spaceship landed in Smallville during the meteor shower.

As a massive tornado rumbles towards an unsuspecting Smallville, Clark is on the verge of discovering the first connection to where he came from when the missing piece of the spaceship is found and breathes life into the fallen craft. Meanwhile, Lex is hit with a one-two punch after his father closes the plant and orders him back to Metropolis and the shifty reporter he hired to spy on the Kents discovers Clark's superhuman abilities and the spaceship hidden in the storm cellar.