Season 1

Brian Moser

The first season of Dexter introduces Dexter Morgan , a blood-spatter analyst for the Miami Metro Police Department who secretly lives a double life as a vigilante serial killer. He follows a strict moral code taught by his adoptive father, Harry Morgan, which dictates that he only kills criminals who have escaped justice.

Throughout the season, Dexter struggles with his lack of emotions and his need to kill while maintaining relationships with his girlfriend Rita Bennett, his sister Debra Morgan, and his colleagues.

The main antagonist of the season is the "Ice Truck Killer," a mysterious and sadistic murderer who drains his victims of blood and leaves their dismembered bodies in unusual locations. The killer seems to know intimate details about Dexter's past, leaving cryptic messages and body parts in places that trigger memories from Dexter's childhood.

As Debra becomes romantically involved with Dr. Rudy Cooper, a prosthetist, it is eventually revealed that Rudy is actually the Ice Truck Killer—and Dexter's biological brother, Brian Moser. Brian wants Dexter to embrace his true nature and kill Debra to prove his loyalty, but Dexter ultimately chooses Debra over him. In the end, Dexter kills Brian, staging it as a suicide.

The season concludes with Dexter reflecting on his double life, realizing that he is capable of making choices beyond his dark urges. The world still sees him as a hero, but he knows the truth of his monstrous nature.