Six months after the season 3 finale, Dexter is now living with three kids and a wife in a new home. Along with his new son Harrison, the complexities of being a suburban father of three is making it difficult for Dexter to concentrate on his work. Dexter's lack of sleep results in a murderer being released because Dexter brought the wrong case file to court. A recently retired Agent Lundy has returned to finally capture the "Trinity Killer", who has been at large for 30 years. After a call from Rita, Dexter quickly kills the released murderer but totals his car after falling asleep at the wheel.