The Secret Circle has found it's John Blackwell! Joe Lando, best known for his role as Byron Sully in Dr. Quinn, Medicine Woman, will play Cassie's aforementioned mysterious father, the source of her ever growing dark magic. Previously thought dead, Blackwell will return to Chance Harbor in episode 15, "Return". He will proclaim to be a changed man, with the safety of Cassie and the Circle as his mantra for returning. Lando's character is described as commanding, enigmatic and powerful witch with many enemies.
Source: TV Guide