Fresh out of jail, Isaak renews his pursuit of Dexter while Quinn continues his power struggle with the Koshkas. Dexter tries to keep Debra in the dark about his relationship with Hannah, but a surprise visit from Astor, Cody and Harrison throws a wrench into his plans.
Dexter tracks down another potential serial killer from Dr. Vogel’s list. Quinn celebrates passing the Sergeant’s exam by defending Debra’s honor in a fight. Dr. Vogel begins treating Debra for her PTSD.
Dexter continues his manhunt for the Brain Surgeon. Dr. Vogel tries to prove to Dexter that he’s perfect as a psychopath. Debra’s PTSD kicks in and she makes a desperate plea to confess to LaGuerta’s murder.
The Ice Truck Killer is back. He leaves a crime scene that brings back some horrifying repressed memories for Dexter. Paul sues Rita for sole custody of Astor and Cody.
Dexter receives notification that his biological father has recently passed away. Dexter is named as the sole heir of all his possessions including his house. Dexter goes for a weekend away with Rita, Deb, and Rudy.
Dexter must do damage control; Debra’s speculation begins to take shape; Quinn becomes involved in a homicide.
Dexter suspects rich women’s shrink of murder. When he visits the shrink, he is surprised by a dark secret from his past.
The police identify the Ice Truck Killer. However Dexter feels there is something wrong with the suspect. Dexter must also deal with Paul, Rita’s recently paroled husband.
Dexter is caught up in a very personal case that awakens the needs of his Dark Passenger; Debra feels overwhelmed by her new Lieutenant duties, made all the more complicated when she finds out Quinn slept with a witness in the Doomsday case.
With the help of his newfound friend Brother Sam, Dexter wonders if there is light within him to counter the darkness, while the search for the Doomsday Killers takes him in a new direction; Batista and Quinn pay a visit to the university where Professor Gellar taught; due to departmental regulations following the shooting, Debra is forced to begin therapy.
