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.