Dexter’s youth story in Dexter: Original Sin begins in 1991. The prequel is set in Miami fifteen years before the first season of Dexter, following Dexter Morgan as he moves from student life toward his career in forensic investigation and vigilantism.
The year places the story in an early stage of Dexter’s development. He is not yet the established blood-spatter analyst seen in the original series; instead, the show explores his first professional steps, his relationship with Harry Morgan, and the process by which Harry helps him channel his violent urges through a code.
The date can be confused with the 2006 premiere of the original Dexter or the later setting of Dexter: New Blood. Original Sin is a period prequel, and its 1991 Miami setting is central to its origin-story premise.