Dexter's worst fears have been realized. Because of Debra's unrelenting pursuit, Miami Metro is just one step away from discovering the identity of the Trinity Killer. And Dexter can't let that happen. Arthur's arrest would not only deprive Dexter of a satisfying kill, it would also expose the secret life Dexter's been leading in his pursuit of this monster. Dexter must take drastic action to buy himself time to deal with Trinity in his own fashion. Meanwhile, Rita decides to confide in Dexter, which doesn't go as well as she'd hoped. LaGuerta and Batista's breach of ethics paints them into a very tight corner. And Arthur, who still can't understand why Dexter didn't simply turn him in, begins his own bloody investigation into Kyle Butler.

Dexter thinks he knows the ins and outs of the Trinity Killer until a 10 year old boy goes missing.

Dexter studies those closest to Arthur in an attempt to understand the psychology behind the Trinity Killer’s actions; Rita’s Thanksgiving-dinner plans are complicated when her full house gets even fuller with the addition of some unexpected guests; Batista sees some closure on a troubling old case; and Debra’s continued pursuit of the Trinity Killer may prove a threat to Dexter.

Dexter learns the Trinity Killer may be taking his act on the road when the homicidal maniac plans an out-of-town trip. To gather more insight into the mind of the murderer, Dexter decides to accompany him, but isn’t really ready for some of the shocking revelations of which he becomes privy. Back in Miami, a technicality is keeping Debra off the Trinity case, but she utilizes others in the department to get her opinions registered

Dexter seems to have finally managed to balance work, family, and his dark passenger. But he knows the balancing act can’t last. A series of murders leads the department to a prominent photographer, prompting Dexter to move him to the top of his list which doesn’t sit well with Harry. But Quinn’s effort to bond with Dexter poses a problem with hunting the new prey. Meanwhile, Debra returns to work and focuses on finding the Trinity Killer, which Dexter fears will put her in danger...

Dexter knows it’s only a matter of time before the Trinity Killer’s latest handiwork is discovered by Miami Metro. He has to work doubly hard to stay one step ahead of their investigation. Debra is shut out from her own case. She considers risking her career and bending the rules in the name of justice. LaGuerta and Batista realize that by playing by the rules they may have painted themselves into a corner. Dexter gleans relationship advice from a most unlikely source when the friction between Rita and Dexter comes to a head....