In the meantime, Vogel and Dexter are hunted by a serial killer, who they initially believe is a former patient of hers. They started to train some random person they initially suspected was the killer, but he was murdered too.
As the show neared its end, Dexter found out the killer is actually his murdered neighbor’s boyfriend and Vogel’s son, Oliver Saxon, who had faked his death in a fire. Vogel initially tried to protect Oliver because she naively thought she could change him, but realized that he’s a lost cause and gave Dexter the go ahead to slice him to bits.
Only it was too late, because Oliver slit Vogel’s throat in front of Dexter, taking away the one parental figure he and Deb had left.
As all of this was going on, Dexter was planning a life in Argentina with Hannah and Harrison. The only thing holding him back is his desire for vengeance. And he nearly satisfies that need when he strapped Oliver down to a table, only to miraculously realize he no longer feels bloodlust.