@Watches Too Much - I don't think Hal knew what was happening, so he wasn't really keeping a secret from Maggie. He seemed to be in a trance like state when he was meeting with Karen. The first sign was when they found the muddy boots.
@Carol - Kadar is played by Robert Sean Leonard. He's probably best known for playing Dr. Wilson on House. He also was in Dead Poet's Society.
@Kevin - In an interview with Noah Wyle, he said the series won't have longer seasons. He likes the short season because it's not too disruptive to his family life.