Kevin Grady commits thefts and uses his superpower to delete the incident from witnesses' minds. When he does so with Clark who stopped him after robbing The Talon, much more memory gets wiped, so Chloe must take super-boy home to the Kent farm and help him remember who he is, including discovering together the amazing extent of his superpowers and his feelings for Lana Lang. Meanwhile Lana tells Jason she's neither sure she still wants to go to college nor to stay his girlfriend, claiming it's not Clark but their complicated past, he walks off angry, warning she doesn't realize how much he has been protecting her. Clark and Chloe trace a motor-park pass Kevin dropped to his home, or rather to his father Lawrence Grady, and gradually discover Kevin is in memory manipulation therapy with him in Summerholt neurological institute, where Lex once was a patient, for a hunting accident killing his brother Dillon but escaped. Clark helps Kevin...

When Clark finally discovers Lionel threatened to kill him unless Lana married Lex, he goes after Lionel to silence him once and for all. Meanwhile, Lana tells Lex she is leaving him, and John Jones, the Martian Manhunter, makes a return appearance to help Clark stop Lex, who has captured the last surviving phantom escapee from the Phantom Zone, having possessed a young boy, in order to use its DNA to power him army of super soldiers at his secret lab '33.1'. Clark bids goodbye to Martha as she prepares to leave Smallville for Washington D.C., and Clark finally reveals his secret to Lana to get her to stay in town. But when Lana mysteriously 'dies' in a car bombing, Clark thinks Lex was behind it and sets off to kill him, and has a fateful meeting with the last wraith of the Phantom Zone at Lex's 'Project 33.1' lab at Reeves Dam. Lois goes to Reeves Dam in search of information about Lex's secret lab and is brutally stabbed by a security guard. Chloe finds a piratically dead Lois at the dam where in a moment of weakness, Chloe's secret power is finally revealed.

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, searing the machine with heat vision, he also falls victim to the serum and sees what Kara sees: his mother.

Oliver returns and enlists Chloe in his vendetta against Lex, but a sexy new 'superhero' stands between Oliver and his mission, even if Lex is, ultimately, one of the bad guys.