He'll charm fellow officers with doughnuts, spend a Sunday doting on his young son, Harrison, or chop up a victim and toss the parts off the side off his boat. Hiding beneath the mundane exterior of Dexter, a seemingly shy blood spatter expert for the Miami police, is an obsession with meting out his own twisted brand of justice. Dexter kills according to a strict code established by his late father, Harry. But Dexter's carefully ordered reality is crumbling now that his sister Debra knows all and has become his unwilling accomplice.
While it's a dream come true for Debra to be promoted to Lieutenant, it hasn't all been smooth sailing for Dexter's adopted sister; she ended her relationship with Quinn, sought therapy for the stresses of her job, and realized the love she felt for Dexter wasn't just platonic, it was romantic. But that was before she saw Dexter doing what he does best: slaying a serial killer. Debra is torn between her brother and her badge, and only time will tell how she's able to deal with this shocking revelation and the dark memories it brings up.
Miami Metro's roguishly charming Detective Quinn has always made questionable romantic choices. He was heartbroken when his boss Debra turned down his proposal, then found love in the form of an illegal Ukrainian stripper who fled Miami with his help. He has now turned his attentions to Jamie, his new boss Angel Batista's sister and also Dexter's nanny. He's treading in dangerous territory again, especially since Batista is trying to get him promoted to Sergeant.
Always quick with an inappropriate remark, Masuka is the wisecracking Miami Metro forensic investigator who works alongside Dexter in both the lab and in the field. A master of both innuendo and crime scene investigations, Masuka may hit on anything that moves but he's essentially harmless and can be counted on for real emotional support when the time calls for it.
A fellow homicide detective, Angel Batista works closely with Dexter and the team on their various forensics cases. The big-hearted Batista took it in stride when Debra was promoted to Lieutenant instead of him, and toyed with the idea of retirement when he bought a beachfront restaurant. But since Debra left the force, he is now the Lieutenant in charge of Miami Metro Homicide, postponing his retirement indefinitely.
Harry Morgan, Dexter's adoptive father and a former homicide detective, was first to spot Dexter's passion for human vivisection and helped his son channel his homicidal impulses into a more constructive pursuit: vigilante justice. Long dead and now appearing only to Dexter in visions, Harry tries to keep his twisted son on the path he set for him via the Code: a set of rules Dexter must live and kill by. But after Debra caught him in the act, Dexter broke one of Harry's most important rules, that no one else must ever know his secret.
An old time homicide detective with questionable ethics, Matthews was friends with Harry and has known Dexter and Debra since they were children. Disgraced and forced into early retirement by LaGuerta, he agreed to help her pursue Dexter in return for his honorable reinstatement.
Angel Batista's sister Jamie has been working for Dexter as his son Harrison's nanny ever since Dexter's wife Rita was killed. Kind-hearted, loyal, and devoted to Harrison, she is invaluable to Dexter. Her brother, Angel Batista, has always been over-protective of her, and her new romance with Quinn threatens to strain their relationship.