A kryptonite-based explosion at the Luthorcorp lab creates an evil clone of Lex, and the sinister twin tries to prevent the process from being reversed by taking drastic measures, which include imprisoning Lex in the basement of his own mansion.

Clark's entire memory ends up getting erased when he confronts a thief who has a kryptonite-based ability to wipe out people's short-term memories. As Clark learns about his life, he's shocked to discover that he has superpowers.