Dexter sleeplessly struggles to balance his new family life with his dark, murderous drive for a fresh victim, and his busier-than-ever forensic career pursuing a new target, "The Trinity Killer."

Suffering from amnesia following his car crash, Dexter begins searching for Benny Gomez' lost body, with a helping hand from Harry. Meanwhile, Debra struggles with the return of her former lover while Quinn tries to juggle his personal and work life. Meanwhile, Trinity begins stalking his next chosen victim.

Dexter is hampered by his neighborhood's increased vigilance due to vandalism, his temporary inability to drive himself anywhere, and his admiration for the killing technique of the artful Trinity Killer.

Dexter gets some much-needed R&R time with Rita and the kids out of town, leading to his stalking of a new victim until he unexpectedly begins to empathize with his target, a cop that murdered her family.

Dexter is inspired to investigate the Trinity Killer on his own, while Debra blames herself for an event that was out of her control, and Rita realizes how little she knows her husband after discovering one of his secrets.

Dexter doubles his efforts to stay ahead of the official Trinity investigation, and receives relationship advice about the friction between himself and Rita from a most unexpected source.

Dexter finally strikes a balance between family, career and his secret life, but is thwarted in his pursuit of his next victim, while Debra expresses a renewed and unwelcome interest in their father's checkered past.

Dexter wonders if his father's Code is truly the right path, and hopes to get answers by accompanying Trinity on an out-of-town road trip, while Debra discovers that her single-minded pursuit of Trinity has blinded her to the truth.

Dexter finally believes he understands the beast known as Trinity. But when a ten-year old boy goes missing, Dexter is forced to question everything he’s learned up to this point.

Dexter must buy time to protect himself when Debra's investigation brings the department one step away from identifying Arthur as the Trinity Killer; Rita confides in Dexter, but is disappointed in the result.

Dexter and Arthur find themselves on a collision course, as Debra unearths a shocking long-hidden truth, Rita admits her marriage to Dexter is troubled, and Batista and LaGuerta face the consequences of an ethics breach.