- Directors: Patrick Tatopoulos
- Producers: Len Wiseman, Tom Rosenberg, Gary Lucchesi, Skip Williamson
- Writers: Len Wiseman, Danny McBride
- Genres: Action, Fantasy, Horror, Thriller
- Actors: Bill Nighy, Michael Sheen, Rhona Mitra, Kevin Grevioux, Steven Mackintosh, and Kate Beckinsale
The film tells the story of the origins of Lucian (Michael Sheen), who was the first werewolf able to take human form – to be called Lycans. Viktor (Bill Nighy), the ruthless elder of the vampires, took him home after killing his werewolf mother in a raid. Viktor envisions a race of werewolf slaves for his vampire clan that, conceivably, could keep guard during the daytime hours and toil for the vampires. As Lucian grows up at Viktor’s home, his young daughter, Sonja (Rhona Mitra), develops an attraction to the young Lycan, and Lucian becomes fond of Sonja as well.
It is revealed that Viktor has a tacit relationship with the human population of the area, whereupon he agreed to protect them from the wild werewolves that roam the countryside in exchange for a tithe. As a collection of human nobles come to meet with the vampire council for protection from the werewolves in exchange for this aforementioned tithe, Sonja goes out to guard them. Lucian hears the Lycans near Sonja and steals a horse and sword from a nearby Death Dealer. Wild werewolves proceed to attack and kill the nobles, causing Lucian to engage in a battle with them. When Lucian takes off his collar and changes into a Lycan in order to protect himself, the wild werewolves back down to his howl and leave before Lucian is shot down by Viktor’s men. Viktor, despite grudgingly acknowledging that Lucian saved his daughter, notes that Lucian still transgressed the laws of the coven by taking off the collar that kept him in check (by preventing him from changing into a Lycan) and feels betrayed by what he thinks of as his favorite pet. Subsequently, he locks Lucian away after having him whipped thirty times with a three pronged chain-bladed whip.
The film ends with the opening scene of the first Underworld, with the audio from the scene where Kraven tells Selene that it was Viktor who murdered her family, rather than the Lycans. That Viktor spared her because she reminded him of Sonja, the daughter he condemned to death.