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 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.

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.

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 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 must save a life; Deb has a confrontation with a key suspect; Quinn follows up on the similarities between Dexter and Kyle Butler.

Dexter finds himself teamed up with a fellow Dark Passenger when he takes a road trip to Nebraska to tie up some loose ends from the past; Debra deals with the complications of her promotion as she leads the Doomsday investigation.