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.

Dexter figures out who the Ice Truck Killer is, along with a dark secret from his troubled past. Meanwhile, La Guerta is replaced with a new boss and Angel figures out a way how to track the killer while he's still in hospital.

Miami Metro is just one step away from discovering the identity of the Trinity Killer. And Dexter can't let that happen. Dexter must take drastic action to buy himself time to deal with Trinity in his own fashion. Arthur, who still can't understand why Dexter didn't simply turn him in, begins his own bloody investigation into Kyle Butler.

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.

For most people, Thanksgiving is a time for traditions and family. But for Dexter, it’s an opportunity to get closer to his most dangerous adversary yet. As Dexter gains insight into Arthur’s psychology by studying those closest to him, he finds himself drawn into a bizarre and twisted world.

After witnessing her brother kill Travis Marshall, Debra attempts to reconcile with Dexter while struggling to cover up their involvement with the murder. Meanwhile, Detective Mike Anderson has an unfortunate run-in, Quinn and Batista begin to make amends, and LaGuerta finds evidence that causes her to re-think the closed Bay Harbor Butcher case.

Dexter must protect himself when LaGuerta closes in on his secret.

The Ice Truck Killer sets a trap for Dexter by kidnapping someone close to him; Dexter's increasingly odd behavior piques Doakes's interest.

Lila Tournay finds Sgt. James Doakes imprisoned in an Everglades cabin and learns from him that her object of affection, Dexter Morgan, is the serial killer known as the "Bay Harbor Butcher". She decides to help Dexter and kills Doakes by setting the cabin on fire. Meanwhile, Dexter's sister Debra questions whether her career is more important than her relationship with FBI Special Agent Frank Lundy.

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 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.

The Ice Truck Killer prepares a crime scene for Dexter: a hotel room all covered in his previous victim's blood. But Dexter does not appreciate this gift, because his childhood memories hunt him.

Dexter and Homicide race against a lunar eclipse to catch the Doomsday Killers before their final gruesome act; Debra struggles with a new emotional reality.

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 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.

A series of chess-like moves ensues when Dexter and Miguel vie for the upper hand, with Miguel winning Rita's affection by presenting her with a lavish wedding gift. Elsewhere, Debra wonders if her relationship with Anton is worth the trouble.

The Ice Truck Killer leaves a clue at the scene where Dexter has dispatched his latest victim, and Dexter is worried that someone might have witnessed his killing. Rita is trying to deal with her ex-husband.

Dexter appears to be connected to a psychiatrist suspected of murdering a suicidal patient.

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.

Recent events spur Dexter into his own investigation of the Trinity killer. His motivations are now personal, and the clock is ticking. But the closer Dexter gets, the more he realizes that Trinity is unlike any monster he’s previously encountered. Meanwhile, Debra blames herself for events that were out of her control, and in so doing pushes away those closest to her. As LaGuerta and Batista close in on the Vacation Murderers, Batista realizes he can use Quinn’s relationship with a certain reporter to his advantage. And when Rita discovers a secret Dexter’s been keeping from her, she begins to realize just how little she knows about the man she married.

Dexter and Lumen hunt for their next victim; Debra uncovers new evidence in the Barrel Girl case

Homicide uncovers some key evidence linked to one of Dexter's and Lumen's prior victims; Debra identifies two more suspects in the case.

It's Christmas time, and Debra learns it may be better to receive when she gets a tip from Hannah's father... one that could lead to incriminating Dexter in a crime. Meanwhile, Dexter discovers that the man behind his mother's death has been released from prison.

While preparing for his big wedding day, Dexter has to figure out a way to remove Miguel from his life for good. In the meantime, Rita has troubles of her own, when Syl reveals that Miguel has been seeing one of his old flames. Debra finds a new clue that brings her even closer to catching the Skinner.

It is the day before Dexter's wedding and Dexter must deal with two people targeting him, while preparing for his special occasion. Meanwhile, Angel tells Deb he's put her in for a promotion, but after he finds out some information her shield may be gone before she gets it.