Eph and Fet recon for an all-out assault that Setrakian assures them will finally kill the Master. Gus aligns himself with a strange new force, one that may swing the fight in an unforeseen direction.

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.

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.

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.

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.