Still trying to come to grips of the fact that Dr. Vogel is dead, Dexter wants to finally get rid of Oliver Saxon before he, Hannah and Harrison leave the country for Argentina. He also has a lot of personal loose ends that he needs to tie up, including selling his condo. Saxon show’s up at Dexter’s condo as a prospective buyer and gives Dexter a deal: They stop trying to kill one another and they go their separate ways. Saxon gave his mother a choice between him and Dexter and when she chose Dexter over her own son, that is when he decided to kill her for his own purification purposes. Saxon tells Dexter that if he does not agree to the terms which he has placed in front of him, Saxon will go after Dexter’s family and kill them. Dexter is quite apathetic and having found Saxon’s killing room, Dexter has set a trap for this monstrous murderer. Debra drops by Dexter’s condo with something to eat and begins to give him the rundown on Saxon. Dexter tells his sister to leave because he is “expecting money” but she locks the door and tells him that nothing will get in the way of spending one more night with her brother. Quinn receives the report that the DNA is in fact the proof that Saxon is Vogel’s son. Meanwhile, the U.S. Field Marshal is tailing Deb, quite certain that she will lead him to the whereabouts of Hannah.
Having made the agreement to move to Argentina with Hannah and Harrison, Dexter has a lot to accomplish before he sets out to make a new life with his new family. He confides in Deb about his plans, but it turns out she isn’t very pleased with what she is hearing and the conversation does not go over well. Turns out that the man Cassie was dating, Oliver Saxon, is in fact Vogel’s son Daniel. Dexter heads to over to Vogel and tells her that Saxon, her son, is very dangerous and she is in desperate need of protection. She tells Dexter that he needs to take a step back and let her deal with this in her own way, but Dexter has no purpose leaving Miami while Saxon still breathes. Saxon abducts his mother and places her in his killing room, telling her that it is exactly identical to the treatment room that she had placed him in thirty-seven years ago. He wants his mother to assist him in the same way that she has guided Dexter. She agrees to this and tells him she will figure out a way to help and she will speak with Dexter. Meanwhile Quinn advises Jamie that she should at least go to a job interview for a great position at a well-known academy in Atlanta, Georgia. Masuka gets quite the shock and disappointment when his daughter shows up to a crime scene under the influence of drugs.
Dexter has decided that he wants to make a new life for himself with Hannah and Harrison but not before he has dealt with the murderous monster Brain Surgeon. While searching Zach Hamilton’s art studio, Dexter finds blood and a clump of hair underneath a desk. When Dexter takes it in and runs a DNA scan, he comes to find out that the blood belongs to someone who is related to Dr. Vogel. While quite skeptical of his findings he tells Vogel that the Brain Surgeon is somehow related to her. Vogel sits Dexter down and explains that she once had two sons. One of which, Daniel, killed his younger brother. He was placed in a mental institution but died from a fire in the institution when he was only 14. Dexter strongly believes that he survived and quickly has him singled out. Dexter tells Vogel that her son is still alive and Dexter plans on killing Daniel. She admits that she is a bit conflicted with this fact and tries to convince Dexter that Daniel needs a second chance. Dexter goes along with it and asks for assistance in finding him. He finds out that Daniel has been monitoring his mother on her laptop with spyware. Deb begins to have doubts and second thoughts about returning to Miami Metro Police. She has also allowed Hannah, who is now being hunted down by a Federal Marshal, to hide out at her house.
Dexter is quite certain that it was Zach who bludgeoned Cassie to death in her apartment. It seems as though it was an impulsive murder rather than planned out like Norma Riviera’s murder. Dexter comes to find out that it is Zach’s blood under her fingernails and does not report it to the police for obvious reasons. Dexter tries to keep the police off of Zach’s tail. Dexter and Vogel converse about how they can not find Zach and he blames her for Cassie’s death due to the fact she talked Dexter out of killing Zach. Zach ends up in the Florida Keys. Dexter finds this out because Zach has used his credit cards down there. Dexter and Hannah pack up to go and find him. What Dexter finds impresses him but also indicates that Zach is not the killer of Cassie. Dexter finds Zach dead with a large portion of his skull missing which indicates that it is the Brain Surgeon behind all the murders. Vogel is now in possession on a chunk of Zach’s brain, just like all the other victims. All the while, Dexter is in the process of helping Hannah obtain a new identity and making plans to get her out of the United States. Although during this process, Dexter begins to see that the bond he shares with Hannah is becoming quite strong and he begins to start seeing a different future for himself, possibly with Hannah in it.