JONATHAN KENT RETURNS — Still distraught over her break-up with Clark (Tom Welling), Lana (Kristin Kreuk) experiments with a dangerous serum that allows her to flat-line and see her deceased parents again. A worried Clark rushes to save Lana from hurting herself, but ends up being injected with the kryptonite-laced serum by a rogue doctor (Patrick Currie). When Clark flat-lines, he is able to talk to his father, recently deceased Jonathan (John Schneider), who warns him that Lionel (John Glover) knows his secret.. Meanwhile, Lionel continues to get closer to Martha (Annette O’Toole). Michael Rosenbaum and Allison Mack also star. The episode was written by Holly Harold and directed by Jeannot Swarc (#2T6417).