Smallville - Season 4 Episode 19 : Blank 2011

When a boy who can make people lose their memories robs the Talon, Clark goes after him but gets total amnesia. Chloe finds out what happened and has to tutor Clark in the use of his superpowers and make sure he doesn't accidentally reveal his secret. While Clark, Chloe, and Lois try to track down Kevin, Clark takes advantage of his "new life" to ask Lana on a date. And Lex tries to turn Clark's memory loss to his advantage by getting him to reveal the secret of the caves.