The Dexter writers certainly have focused on episode-ending cliffhangers this season: Dr. Vogel knows about Dexter’s code. Debra drives into a lake with Dexter as a passenger. And, last week, both Deb and Dexter pass out after drinking wine, laced with a knockout drug by the unexpectedly reappearing Hannah (Yvonne) Strahovski, the poisonous yet alluring serial killer with whom Dexter has shared a torrid affair: on-again, off-again, maybe-I’ll-off-her, maybe-I’ll-off-him.