At three years old, Dexter witnessed their mother, Laura Moser, being brutally murdered with a chainsaw by drug dealers in a shipping container. Dexter was left sitting in pools of his mother's blood for two days before being discovered. Miami Police officer Harry Morgan rescued Dexter and arranged for him to be adopted into his own family. As a child, Dexter exhibited troubling behavior, including killing and dismembering animals. Recognizing that Dexter's homicidal compulsions could not be cured or suppressed, Harry chose to train him. Harry established "The Code," teaching Dexter to channel his dark passenger exclusively into hunting and killing heinous criminals who escaped the legal justice system, while meticulously avoiding detection through forensic science and disposal at sea. When Harry discovered one of his hospital nurses, Mary, was intentionally poisoning him with morphine, he gave Dexter "permission" to perform his very first planned kill on her. Harry died a year later when Dexter was 20, though wracked with guilt over what he turned Dexter into when Harry took his own life after walking in on Dexter brutally dismembering a drug dealer named Juan Ryness, forcing Harry to confront the grim reality of the monster he helped create. But Dexter only thinks he died of heart disease, because that’s what Harry made everyone around him tell him. Dexter only targets murderers and dangerous criminals who have slipped through the legal system. He investigates his targets, follows their routines, and gathers physical proof of their crimes to confirm their guilt before moving in. He sneaks up behind the victim and injects them with M99 (a powerful animal tranquilizer) to knock them out instantly without a struggle. He builds a sealed "kill room" lined entirely with plastic sheeting to catch any blood or evidence. He straps the unconscious victim to a table and wakes them up. He shows them photos or proof of their past murders and forces them to face what they did. He makes a tiny cut on the victim's cheek using a scalpel to collect a single drop of blood on a glass slide, then puts that slide in a box that he hides in his air conditioner. He usually kills the victim by driving a knife straight through their heart, though he occasionally uses a scalpel or blade on the neck if needed. He cuts the body apart, seals the pieces in heavy black trash bags, and cleans the room completely. He dumps the bags into the ocean from his boat. Dexter Morgan is a meticulous, highly intelligent forensic blood spatter analyst, who often exhibits autistic traits like his inability to read sarcasm and social cues, but he is a sociopath. Dexter Morgan is 5’11ft tall, lean, and very physically fit from an active lifestyle. He has short auburn hair, often neatly styled or parted. He has intense hazel eyes. He maintains a meticulous, conventional look for his work as a blood spatter analyst, frequently wearing casual button-downs or brightly colored Hawaiian shirts in his day-to-day life.

She is the adoptive sister of Dexter Morgan, raised by their parents Harry and Doris Morgan. Growing up, she struggled with feelings of insecurity and often felt jealous of the intense attention her father, Harry, gave to Dexter. She is intensely driven, aggressive, and determined to prove herself in a male-dominated field. Beneath her tough, cursing exterior lies deep self-doubt and an emotional need for validation, especially from her adoptive brother Dexter. She often acts on gut reactions or raw emotion, leading her into chaotic situations and messy relationships. Known for her frequent and creative use of profanity, which contrasts sharply with her professional environment.

She begins as Lieutenant and the head of homicide at the Miami-Metro Police Department. She is ambitious, politically savvy, highly intelligent, and willing to use manipulation or ambition to climb the ranks. She serves as the superior officer to Dexter and Debra Morgan. She is a Cuban-American woman with dark brown hair, expressive dark eyes and a sharp commanding presence.

He constantly drops tasteless, sexually explicit jokes, even while standing over dead bodies at crime scenes. His high-pitched, awkward snicker is his signature reaction to his own jokes. He feels completely comfortable in his own skin and never apologizes for who he is, regardless of how uncomfortable he makes his coworkers. Behind his perverted exterior, Masuka is an elite forensic scientist who relies on hard evidence, physical facts, and a methodical process of elimination. He is of Japanese descent, of short to mid-height, with an average build He is clean-shaven with a bald or closely shaved head. He typically wears prescription glasses and frequently sports either a thoughtful, serious frown or a wide, perverted grin accompanied by his signature laugh.

 Angel Batista is a friendly, good-natured, and compassionate homicide detective Angel Batista is a middle-aged Hispanic man.

Sergeant Doakes has a volatile temper and an abrasive communication style. He frequently clashes with coworkers and is famous for his blunt, unfiltered delivery. A former Army Special Forces operative and Ranger. He stands roughly 5'8ft, has a strong, muscular physique, and is African American.