The novel continues the tale of Dexter Morgan – serial killer with a code of honor. It picks up where the previous novel left off – the aftermath of the murder of Detective Laguerta at the hands of Dexter’s long-lost brother Brian.
The detective’s death confirmed the suspicions of Dexter’s long-time enemy sergeant Doakes and the latter decides to tail Dexter, night and day, until he finally catches him at the act. This prevents Dexter from engaging in his usual proclivities, forcing his disguise, his “daytime persona” to become his reality. Dexter starts spending a lot of time at his girlfriend Rita’s house, and bonding with her two children, Astor and Cody. As the novel progresses, Dexter discovers that they are just like him – traumatized children who as a result developed homicidal tendencies. He resolves to try to train them as Harry had trained him, to become careful killers, and to kill only people who definitely deserve to die.
As Dexter slowly grows desperate with his desire to arrange a “playdate” with a murderous pedophile whose accomplice he had already caught and dispensed with, he and his sister Deborah are called to the crime scene of a truly grisly act – a victim, barely alive, left in an unoccupied house. The victim’s limbs were all amputated, along with anything that made him remotely recognizable – the nose, ears, lips, eyelids, genitals. The only clue found next to the victim is a piece of paper with the word “LOYALTY” written on it, with all the letters crossed out. When Doakes arrives at the scene it becomes obvious that he knows something about it.
The case is quickly transferred to a government official, Kyle Chutsky who immediately hits it off with Deborah, and the two start going out. Meanwhile, Dexter finds out that Doakes is familiar with the almost-killer from his army days in El Salvador, where Chutsky also served.
After several attempts by Chutsky, Deborah and Dexter to locate the perp who goes by the name of Doctor Danco, Chutsky himself is kidnapped by Danco. Deborah receives his pinky in the mail, still wearing his distinctive pinky ring. A replacement is sent from Washington, but he is also kidnapped and murdered. His mutilated corpse is discovered in an abandoned house, with a piece of paper bearing the word “POGUE” on it, the letters crossed off again.
After Dexter obtains Chutsky’s ring back from evidence for Deborah, he goes over to Rita’s house, where the ring is discovered and Rita mistakenly assumes it’s an engagement ring. Dexter couldn’t find the words to explain the error, and became engaged to Rita.
Deborah gets Dexter and Doakes to work together in order to find Dr Danco and rescue Chutsky. After chasing one of Doakes’s and a run-in with the Doctor, which leaves Deborah in the hospital with a broken collarbone, Dexter and Doakes discover that Danco is using a police scanner to keep track of Doakes’s movements. They decide to use the police scanner to lure Danco into a trap. They let him know that Doakes will be at Dexter’s engagement party. At the party, the plan to trap Danco fails, and Doakes is kidnapped. Dexter follows Danco to an Alligator farm where he finds Chutsky, minus and arm and a leg. He brings him back to Miami, and for a while slips into a peaceful existence without Doakes. But Deborah solicits his help with finding Danco once and for all.
After some initial resistance, Dexter agrees to help. Through a lucky stab at one of Danco’s potential future victims, Dexter finds the doctor, and calls Deborah and Chutsky. Unfortunately, Dnco spots Dexter and drugs him. Dexter wakes up tied to a table. He sees Doakes, who is already missing some of his extremities, and realizes that Danco plays “hangman” with his victims, and that he severs a body part with every wrong guess. He banters with Danco, despite feeling less than confident about his chances of survival, and then Deborah and Chutsky storm in. Deborah kills Danco, and frees Doakes. Because of his sustained injuries, Doakes would not be able to stalk Dexter anymore.
The novel ends with Dexter on his boat, as he gets rid of the remains of the pedophile he had been hunting in the beginning of the book. Dexter remarks that he feels great contentment and hope for his future as father to Cody and Astor.