From readingeagle.com:
"Fans of "The Secret Circle" are also aware of another pivotal relationship involving Diana: Her father, Charles (Gale Harold), ignited the house fire that killed Cassie's mother, which resulted in Cassie's arrival in Chance Harbor. ...
"There's so much about Charles that Diana doesn't know yet," Hennig said. "I know because I read the scripts, but I can't wait for the day when Diana finds out who he really is. I think it'd be a great story line for Diana to find out what Charles has been up to. Diana could spiral down into a psychotic phase. I do hope that we'll see more of Diana and Charles, but I know you'll see more of Charles on the show, and Gale is so good.""
Hennig bewitching in her role on 'Secret Circle'