Having been caught in the act of eliminating Travis Marshall by his sister Deb, Dexter has to scramble to come up with an explanation. Deb is understandably shaken by what she's just seen but accepts, somewhat reluctantly, Dexter's explanation that he's suffered momentary madness. As she thinks about it, Dexter's explanation makes no sense and decides to dig deeper. Captain LaGuerta meanwhile is puzzled by a piece of evidence she found at the scene of the Marshall killing. When a member of the homicide squad is killed, Dexter goes all out to stop the killer before he ...

With Deb keeping a close eye on him, Dexter is starting to go stir crazy. He desperately wants to satisfy his dark passenger but first decides to get Louis Greene out of his life forever. Deb is growing increasingly frustrated at the lack of progress in finding Mike Anderson's killer. The murderer's employer, Isaak Sirko, is having much better luck and actually traces his former employee right to Dexter's boat. Dexter wants to kill someone and focuses on the recently paroled killer Ray Speltzer. Dexter is convinced that Speltzer will kill again and tries to convince ...