10 Small Details You Only Notice Rewatching Dexter
7. Left Turn Ahead
In the penultimate episode of season two, one of Dexter's co-workers has found out his true identity as "The Bay Harbour Butcher." Sgt James Doakes has been suspicious for a long time and eventually found enough evidence, but Dexter has captured him and locked him up.
He is very close to accepting Doakes' advice to turn himself in, spending one last day of freedom with Rita and her children and daydreaming about what would happen if he were to confess his crimes to Debra.
In the end, none of this comes to pass, as the cabin where he is being held is blown up and Doakes passes away. Instead of Dexter's whole secret life being unravelled and his secret exposed, it is now assumed that it was Doakes who was the serial killer all along.
During one of their exchanges however, the Sergeant tells Dexter that this "darkness" inside of him will harm Rita, her children and Debra if he doesn't turn himself in. Obviously, Doakes does not live to see this prophecy come true but Debra and Rita both die as a result of their association with Dexter and Rita's children are left abandoned in the end, much like Dexter himself was.