And then another genetic fluke transformed the balance of power again: a female werewolf, captive in the Vampire stronghold, gave birth to a seemingly human child. This was Lucian (Michael Sheen) – the first Lycan, born into slavery in the house of Viktor (Bill Nighy), the supremely powerful Vampire leader. Unlike "William's Kind”, the original werewolves, this Lycan was able to take the form of either man or beast at will. Lucian's bloodline was used by Viktor to create an entirely new breed of slaves, abused by the Vampires as laborers and guards during the vulnerable daylight hours, and prevented from transforming by the silver-spiked moonshackles kept locked around their necks.

Viktor reigns over his slaves, his court and his domains with an iron hand. He loves only two things: power, and his beautiful but willful daughter Sonja (Rhona Mitra).

Each night, Sonja rides with the Death Dealers, an elite squad of Vampire soldiers that protect Viktor's domain against the marauding werewolves. But unknown to her father or any of her peers, Sonja has fallen in love with Lucian, now a skilled blacksmith and weapons-maker in the Vampire castle. Their affair must be conducted in the utmost secret, since if discovered, it would mean certain death for both of them.

When Lucian reveals that he has found a way to remove his moonshackle and gain his freedom, Viktor resolves to destroy him like a disobedient animal. In a thrilling sequence, Lucian manages rally the other Lycans and escape from the Vampire dungeons - with Sonja's help.