Believing that key information about his father's past was lost when his memory was erased, Lex decides to join an experimental program with Dr. Garner 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 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.
Elenco: Tom Welling , Erica Durance , Allison Mack , Aaron Ashmore , Annette O'Toole , Callum Blue , Cassidy Freeman , Eric Johnson , James Marsters , Jensen Ackles , John Glover , John Schneider , Justin Hartley , Kristin Kreuk , Laura Vandervoort , Michael Rosenbaum , Sam Witwer , Samuel L. Jones .