Dexter: Original Sin Season 1 ending explained: Did Dexter kill Spencer?

Showtime's Dexter: Original Sin has wrapped up Season 1, with the finale airing on February 14, 2025. The season has effectively captured the beloved serial killer's origin story in detail.

One of the most shocking inclusions this season was the storyline of Dexter's brother Brian, or The Ice Truck Killer, who had a confrontation with Harry in the season finale.

In the past episodes of the season, Harry was investigating the NHI Killer. He was sure that Brian Moser was behind the murders, and that he had killed Barb. In the final episode, Harry confronts Brian, who accuses the former of separating him from his brother. Harry asks Brian to surrender for all the murders. Elsewhere, Dexter saves Nicky and kills Spencer in the season finale.

Here is the complete recap of Dexter: Original Sin Season 1 finale, with the ending explained.

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What happened to Captain Spencer in Dexter: Original Sin Season 1 finale?

The major resolution that fans were waiting for in the Dexter: Original Sin finale revolved around what would happen to Captain Spencer. After thinking that he had an upper hand and was able to escape Dexter, he ran straight to an abandoned ship, where Spencer had kept Nicky.

Dexter was chasing him, and he managed to get hold of Nicky's location. However, Spencer was not an easy adversary. He opened the chamber's water line where Nicky was held, putting the boy in peril.

Spencer offered Dexter with two choices — to save Nicky before the chamber was flooded or catch him. Dexter chose to save the child first and later call the police.

He then sets off to catch Spencer, who is headed for his ex-wife's house to kill her and her new husband. There, we learn that Nicky is not Spencer's child. He was the born after the affair Spencer's wife had with her new husband.

After learning Spencer's secret, Dexter takes him out on Camille's boat to kill him. Here, Spencer tries to manipulate him by saying that Dexter might also be an illegitimate child, born out of the love affair between Harry and his mother, Laura, Dexter keeps his vigilante focus and kills Spencer in the Dexter: Original Sin finale.

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The Morgans enjoy family time in the Dexter: Original Sin finale. Will Brain Moser return in Season 2?

After Dexter kills the child killer in the Dexter: Original Sin finale, he returns to his house, where Harry is watching the news about Spencer on TV. Dexter tells Harry that he has killed Spencer, and is proud that their code is finally working. Dexter now kills only the people who deserve the fate.

The Morgans go on a family lunch, where Debra announces that Tanya and Camille have inspired her to go to the Police Academy. She wants to start with the Miami Police Department. Season 2 might explore more of Deb's character as fans seem to have loved her in Season 1.

Brian's chapter might not be over, even after his encounter with Harry in the Dexter: Original Sin finale, because in the episode's final moments, he was shown lurking in the shadows and watching Dexter with his family.

This ending hints that Brian might come after Dexter or Harry if and when the show is renewed for Season 2.

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