Eph and Nora work on a biological weapon to kill the strigoi, and Setrakian risks the lives of the entire group to find information about a closely guarded secret text. The Master begins the next phase of his own plan, by creating a terrifying new breed of creature and placing them under the control of Kelly.

Eph and Nora experiment on their newfound patients. Fet and Dutch grow closer as they clear out the neighborhood buildings, and Kelly begins her hunt for Zack.

Gus and Vaun wage an attack on Palmer as Eph struggles to connect with Zack. Councilwoman Justine Faraldo vows to bring her extermination policies to the other boroughs.

Eph and Nora finally see their lethal virus in action. Fet takes the security of Red Hook into his own hands while Dutch and Setrakian set off for Staten Island to question Fitzwilliam, Palmer's former body guard.

Eph changes his appearance to leave the city while Nora is left as the reluctant parent for Zack. Dutch and Nora make a deal with Justine to secure Fet's release from jail.

Eph concocts a plan to make and distribute a bioweapon. Gus realizes Angel can be an unlikely ally, and Kelly comes after Nora and Zack.

Setrakian and Fet use Fitzwilliam's info to attack the Master. Eph returns to NYC frustrated but energized to go after the one person responsible for killing his friends.

Eph must protect Zack against a surprise intruder into Red Hook. Gus convinces the Guptas to make a difficult choice. Fet and Setrakian set out to acquire the Lumen.

Justine takes drastic measures to counter a surprise invasion. Nora and Fet perform a useful mission while Eph and Setrakian face off against an old foe.

Eph and Dutch work together to thwart the Master's greatest ally. Justine runs into trouble with the Mayor while Setrakian tracks down the real owner of the Lumen.

Dutch fights for her life against Eichhorst as Fet, Nora, and Eph frantically search the city for her. Setrakian confronts an old acquaintance on his search for the Occido Lumen, while Gus helps the Guptas escape across the border to safety.

Eph must choose between Zack's safety and the safety of the citizens of NYC. Meanwhile, his relationship with Nora reaches a critical impasse, and Gus and Angel assemble an unlikely gang of Sun-hunters.

Setrakian and Fet battle for possession of the Occido Lumen, and gain a surprising new ally. A massive attack imperils Eph, Nora, and Zack's escape from New York.

The strigoi are evolving, becoming faster. Smarter. Eph struggles to improve his failing bioweapon while trying to work through the emotional fallout of the abduction of his son, Zack. As Setrakian and Quinlan attempt to crack the Lumen's deepest-held secrets, Fet helps a Navy SEAL team in a deadly mission: search for the Master through the underground tunnels of New York.

The Master’s offer to return Zack plagues Eph as he considers taking the deal. Dutch reunites with an old group of friends but begins to question if her safety is better with them or with Fet, Eph and Setrakian. Palmer strives for answers to Setrakian’s secret strigoi blood treatments and discovers he may have a way to acquire it.

The Occido Lumen is gone. Stolen. Setrakian and Fet race to recover it. Gus and Angel try to hide a secret houseguest while avoiding a police sweep, and Quinlan's thirst for vengeance is revealed.

Things have changed. The infection enters a new phase. Fet wants to celebrate, but Setrakian and Eph are worried there's more work to be done. Justine conscripts a new, unwilling army in the fight while Eichhorst angrily lashes out with a plan to strike back.

New information from the Lumen forces Setrakian to seek help from his lifelong nemesis, Eldritch Palmer. Eph's new experiments to understand strigoi communication seemingly take him to the brink of madness while Fet is on a mission to discover strigoi movements across New York City.

Fet strikes hard at the heart of the strigoi army while Justine embarks upon a risky mission to drive the strigoi out of Manhattan once and for all. Gus and Angel fight for their lives and their freedom but are faced with a moral dilemma.

Setrakian offers hope in a new plan to trap the Master while Eph and Dutch seek out the Master's “voice.” Palmer needs Setrakian's access to the white to hold up his end of their bargain.

The Master's voice proves to be more powerful and potentially fatal than Eph or Dutch anticipated. Fet and Setrakian track down the cargo from the Egyptian vessel and realize they may be in over their heads. Quinlan strikes a deal with the Ancients, but a last minute betrayal proves deadly.

NYC is falling. Eph and Dutch frantically race to finish their new device to stop the Master before the city is overrun. Justine, Gus, and Angel fight in one last stand to stop the spreading virus. Palmer extracts vengeance for past wrongs but may have crossed the line.

Humanity teeters on the edge of destruction. The Master finally reveals himself, initiating the end game of a battle in which there can be only one winner. Eph, Fet, Setrakian, and Dutch must overcome their personal differences in a last-ditch effort to vanquish the strain.