Season synopsis
Contains spoilers for this season and earlier seasons.
After Debra catches Dexter killing Travis Marshall, she helps burn the church and then learns that her brother is the Bay Harbor Butcher, the killer she has been investigating. She moves him into her home to keep watch, while María LaGuerta quietly follows a blood slide left at the church back toward the old case. Dexter also draws the attention of Isaak Sirko, a Ukrainian mob boss seeking revenge for the death of Viktor Baskov, and meets Hannah McKay, whose history with spree killer Wayne Randall brings her into a reopened Miami Metro investigation.
Dexter discovers that Hannah poisoned one of Randall’s victims, and his attempt to kill her gives way to attraction and a relationship. Her former husband’s death and the poisoning of writer Sal Price expose the danger in that choice. After Hannah poisons Debra, Dexter supplies evidence that leads to her arrest. Meanwhile, Isaak’s pursuit ends after he and Dexter briefly work together against the men sent to kill him: Isaak is wounded by club manager George Novikov and later dies at sea with Dexter. LaGuerta’s investigation grows more focused, even as Dexter and Debra plant evidence to divert it.
After Hector Estrada, the last surviving killer of Dexter’s mother, is paroled, LaGuerta arrests Dexter for his supposed murder, but a decades-old shirt bearing her fingerprints undermines her accusation and he is released. She then finds evidence connecting Debra to the cover-up of Travis’s death. Dexter lures Estrada to a shipping container and kills him, intending to stage a fatal shootout between Estrada and LaGuerta. Debra arrives as Dexter prepares to kill LaGuerta. He drops his knife and offers himself to Debra, but she shoots LaGuerta instead, then breaks down beside her body.