While trying to uncover why someone was killed on his boat, Dexter must out-maneuver a vengeful Isaak. New leads are brought to light on the Wayne Randall case by Hannah McKay, Randall's alluring former accomplice who Dexter discovers has a secret.
Dexter Morgan, a blood spatter pattern analyst for the Miami Metro Police also leads a secret life as a serial killer, hunting down criminals who have slipped through the cracks of justice.
After witnessing her brother kill, Debra attempts to reconcile with Dexter while struggling to cover up their involvement with the murder.
Miami Metro sets out to unearth new evidence on a claim from a local convict that he has new information regarding a 15-year-old crime spree; Debra tries to cure Dexter of his killer tendencies.
Dexter tries to bring Debra on board with his new target. While the Ukrainian mob seeks revenge for the killing of one of their own, Quinn grows close to a dancer at their strip club.
After capturing a deadly killer, things go awry for Miami Metro, sending Debra into a tailspin. In an effort to help his sister, Dexter enters into a dangerous game of cat and mouse, while the Ukrainian mob continues to seek revenge.
While trying to uncover why someone was killed on his boat, Dexter must out-maneuver a vengeful Isaak. New leads are brought to light on the Wayne Randall case by Hannah McKay, Randall's alluring former accomplice who Dexter discovers has a secret.
Debra gets to know a local crime writer who's dug up some incriminating dirt on Hannah McKay. Quinn gets an offer he tries to refuse and Batista is drawn to a new business opportunity. LaGuerta keeps digging into the Bay Harbor Butcher case.
Quinn falls back into his old ways as he makes some questionable choices to protect Nadia. Things heat up as Dexter and Hannah grow closer, but when Sal Price discovers the two are involved, he wants the exclusive story.
Fresh out of jail, Isaak renews his pursuit of Dexter while Quinn continues his power struggle with the Koshkas. Dexter tries to keep Debra in the dark about his relationship with Hannah, but a surprise visit from Astor, Cody and Harrison throws a wrench into his plans.
As Dexter scrambles to track down Isaak, a power struggle erupts among the Koshka Brotherhood, which could prove to Dexter's advantage. Meanwhile, Miami Dade tries to smoke out the Phantom Arsonist.
Dexter is unnerved when Hannah's father pays him a surprise visit; the Phantom Arsonist's crimes become more vicious; and Quinn defends Nadia's honor and finds himself in a volatile situation. Meanwhile; LaGuerta asks a former superior for help on the Bay Harbor Butcher case.
As Christmas approaches, Dexter tries to balance his life with Hannah and his relationship with Debra.
Dexter must protect himself when LaGuerta closes in on his secret.
