Dexter has put his life back together but things may fall apart soon. His new victim is also being targeted by Assistant District Attorney Miguel Prado. Deb has to decide how to handle Internal Affairs, as they want her to turn on her new partner.

Debra and the homicide unit, Dexter and ADA Miguel Prado are all searching for the same serial killer, who is responsible for the death of Prado's younger brother. Meanwhile at home, Dexter is faced with a decision to make concerning Rita and her kid

Dexter and a pedophile have a run-in; Dexter is unable to restore Freebo's good name after he is accused of a murder he didn't commit. Also, Dexter's friendship with Miguel weighs on his mind.

After an unsuccessful marriage proposal, Dexter must convince Rita that he is looking for more than a convenient merger of finances and parenthood.

Dexter hears the story of a husband who has gotten away with murdering two wives for financial gain and tracks the man to Bimini, but Rita has a medical emergency while Dexter has disappeared.

Dexter tests Miguel to see if he is on his dark-side job. Rita questions her career path after being fired from her job. Debra believes she in some way caused another homicide while working on her current case.

Dexter angers Miguel Prado when he says no to his request for them to kill Ellen Wolf. Meanwhile, a deathly ill Camilla Figg asks Dexter to kill her. Anton Briggs is told that he is being used as bait to get at The Skinner.

Dexter undertakes to teach Miguel Prado the Code, but doesn't realize he's whetting his thirst for blood; Debra is one step closer to finding the Skinner; Quinn reveals a secret about C.I. Anton Briggs.

Dexter is happy to have someone to help him with his killings, but can his new accomplice really keep to the Code of Harry or will he become the very thing Dexter seeks to destroy? Rita revolves to confront Miguel about his suspected infidelity. Debra searches furiously for Anton when it's revealed that he was abducted by the Skinner.

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; Debra wonders if her relationship with Anton is worth the trouble.

Dexter must find a way to get rid of Miguel despite the fact that his friend is a highly placed district attorney and also Dexter's best man, and Debra finds a new clue to the Skinner's identity.

Dexter attempts to calm the unstable Ramon now that Miguel is out of the picture; Debra is about to receive her detective's shield but is blind-sided with information that could derail her promotion.