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

Ramon's career may be in jeopardy due to his obsession with Oscar's killer. Meanwhile, Dexter does a great job in keeping Ramon off balance by manipulation. Deb refuses to "be a rat" after Internal Affairs presses her to come up with more dirt on Quinn. Also, Rita and Dexter decide it's time to tell the children about her "condition," and Angel's quest for companionship nearly get's him in deep water.

As Dexter struggles when Rita pushes to move in together before getting married, Miguel tells Dexter that a husband has murdered his two wives for a financial gain and gotten away with it. Dexter finds this to be the perfect candidate to get away and satisfy that dark urge which every man with relationship pressures go through. Dexter tracks the murderer to Bimini. While he is on the hunt, Rita disappears due to a medical emergency. Meanwhile, Debra works with Anton, her confidential informant to track down one of Freebo’s criminal confidants. But Oddly enough Debra finds herself attracted to Anton.

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 when he says no to his latest offer, who's unsure the next target lives up (or down) to Harry's Code. Meanwhile, an elderly, deathly ill Camilla asks Dexter to kill her, insisting she would never ask a friend to do something against his conscience. Also, Rita discovers that Sylvia believes her husband Miguel has had an affair; and Anton is told he is bait to get at Skinner.

Dexter undertakes to teach Miguel the Code, but doesn't realize he's whetting his partner's thirst for blood. Meanwhile, Debra is one step closer to finding the Skinner but a secret revealed about Anton sends him packing.

Miguel and Dexter's friendship is impacted when Rita confronts Miguel about his alleged infidelity. Believing Skinner has abducted Anton, Debra pulls out all the stops to find hi

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.

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.