Believing that key information about his father's (John Glover) past was lost when his memory was erased, Lex (Michael Rosenbaum) decides to join an experimental program with Dr. Garner (guest star Martin Cummins) to regain the information so he can turn his father over to the FBI. Knowing that Lex will discover his secret if he regains his memory, Clark (Tom Welling) tries to stop him but is caught by Lionel and the doctor and exposed to the same radical treatment so that Lionel can solve the mystery of Clark's past.