Dexter is finding it hard to have closure on killing his brother. There is a new FBI agent to head the "Bay Harbor Butcher" case. Debra is finding it tough to put the past behind her.

Dexter's inability to deceive has him pursuing a slick liar as his next victim, while Rita believes he's concealing a drug problem and forces him into a 12-step program where he meets Lila, a seductive new woman.

Rita's estranged mother visits and senses something is wrong with Dexter. Masuka thinks he's developed a lead in the Bay Harbor Butcher case, which has Dexter concerned. Angel's interrogation of a witness crosses a line.

Dexter discovers that the man who murdered his mother in front of him as a boy is still alive and confronts the killer as part of his recovery from addiction - but he also discovers that old impulses die hard.

A copy-cat killer follows the lead of the "Bay Harbor Butcher." Dexter must destroy an incriminating surveillance video.

Dexter manages to get Doakes off his back. He devises a plan to get the police in another direction. Lila and Dex's relationship intensifies, and he has some interaction with Rita and the kids.

Dexter is attacked by the man who murdered his mother. Meanwhile, Lila wants to get closer to Dex, and Debra and Lundy close in on the Bay Harbor Butcher.

Dexter realizes it won't be easy to end things completely with Lila. Dexter tries to stay ahead of the investigations as the manhunt for the Bay Harbor Butcher intensifies. An enemy of Dexter figures out his secret.

Doakes follows Dexter to his next crime scene and shocks him with a revelation about Harry. The Bay Harbor Butcher task force feels they are zeroing in on their man.

Dexter must make a massive decision that will have an effect on all those he holds close. Lila meanwhile is back with a secret to blackmail Dexter.

Special Agent Lundy and the FBI finally settle the case of the Bay Harbor Butcher, but the heat's not entirely off Dexter as the flames literally close in.

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.