WARNING! This article contains SPOILERS for Dexter: Original Sin season 1, episode 9!More of Dexter and Brian Moser’s history comes to light in Brian Moser returns as the NHI killer in Dexter: Original Sin season 1, taking place about 15 years before he’s identified as the Ice Truck Killer and killed by Dexter Morgan. As Harry contends with the knowledge of Brian becoming a serial killer in the present, he also has flashbacks to Brian’s disturbing behavior as a child in the early 1970s.

Following the flashbacks of Laura Moser’s brutal death in the previous outing, Harry’s flashbacks in Original Sin season 1, episode 9 reveal the aftermath of the Morgans bringing Brian and Dexter into their home. While Doris and Harry have grown to love the gentle and soft-spoken Dexter, Brian has violent tendencies that make it difficult to take him in, especially after he tries to suffocate baby Deb in her crib. As the Morgans try to figure out alternatives to keep the boys together, Doris asks about Dexter and Brian’s father, which finally addresses an unanswered question from the original show.

Dexter: Original Sin Confirms Dexter & Brian Have The Same Father

Dexter Finally Confirms That Joe Driscoll Is Also Brian Moser's Father

When Doris asks Barb, who works for the State of Florida while finding a foster home for the boys, about what happened to Dexter and Brian’s father, Barb reveals that he’s in prison and has no intentions of being their father. In fact, he relinquished his custodial rights, which leaves Brian and Dexter without a guardian. Nineteen years after the brothers’ introductions in Dexter season 1, that conversation in Original Sin finally confirms that Dexter and Brian have the same father – a fact that was never clarified in the main series.

Adult Brian’s reunion with Dexter in Dexter season 1 was underscored by the memory of their mother, Laura Moser, with Brian never revealing whether they had the same father. Dexter never even knew who his biological father was until the Ice Truck Killer murdered Joe Driscoll, with Dexter then being notified as Joe’s next-of-kin and executor of his will. Disguised as “Rudy Cooper,” Brian even helped Dexter pack up Joe’s house after killing him back in Dexter season 1, though it’s unclear why Brian wasn’t also listed as one of Joe’s next-of-kin if they were both his son.

Original Sin's Confirmation About Dexter & Brian's Father Changes Joe Driscoll's Death

Brian Killed His Own Father, He Wasn't Just Trying To Get To Dexter

Now that it’s been confirmed Joe Driscoll is the father of both Dexter and Brian, the context of his death in Dexter season 1 is different. Since they might not have been related, it seemed like the Ice Truck Killer had targeted Joe simply to get Dexter to his past and Laura Moser's death, but now it’s clear this was only part of Brian’s motivation. Brian also killed his own father to get revenge for abandoning himself and Dexter, which tracks with why he’s targeting his early victims like Barb in Dexter: Original Sin.

New episodes of Dexter: Original Sin season 1 release Fridays on Paramount+ with Showtime.