Dexter is convinced that Zack Hamilton killed Norma Rivera but has no proof and takes to following him whenever he can. He's more than a bit surprised to follow him to Dr. Vogel's office. She admits that Zach is a new patient but refuses to talk about his case. Batista is under pressure from Deputy Chief Tom Matthews to make a decision on who to promote to sergeant. When Quinn learns he didn't get the job, he redoubles his effort to solve the Rivera murder. With Dexter tagging along, it becomes obvious - to Dexter at least - that Zack is stalking his next victim, ...