Perched on the ledge of a building in a rainy night, two black-garbed "Death Dealers" track a pair of werewolves walking on the street below. Selene and Rigel are vampires that specialize in assassinating an ancient species of werewolves known as Lycans. Selene's motivation goes beyond duty; she also wants revenge, for she believes that Lycans slaughtered her family when she was a child. The vampires believe that they have defeated the werewolves and killed their leader, Lucian, (this is later found to be incorrect) and must now pick them off one by one. As the vampires follow the Lycans into a subway station, the werewolves realize that they are being followed, and they open fire. In the chaotic shootout, Selene realizes that the Lycans may have been following a medical intern, Michael Corvin. After the Lycans retreat from Selene's barrage of machine pistol fire, she tracks them to their subterranean lair, where she hears the sound of a large group of Lycans howling.
When Selene arrives at the vampire coven's ornate, gated mansion, she recounts the evening's unusual events. After the vampire regent Kraven dismisses her fears, and tells her to drop the matter, Selene pursues her investigation alone. She wants to find out why the Lycans were chasing the medical intern, and whether there is indeed a large den of Lycans close to the Vampire coven. Meanwhile, in an underground Lycan lair, a scientist named Singe is testing blood from kidnapped descendants of the Corvinus family, to try and find a pure source of the ancient and powerful Corvinus blood type. Soon after Selene finds Michael, the pair are attacked by werewolves, including Lucian, the original Lycan leader, who bites Micheal on the shoulder. Selene helps Micheal to escape, and the two become romantically attracted to each other.
Selene continues her investigation by breaking into the coven's library to learn about the hidden past of their clan. After she learns from an ancient leather-bound book that Lucian and Kraven formed a pact centuries ago, she awakens a powerful elder vampire Viktor, in the hopes that he will restore order in the coven. As the now-awakened Viktor questions Kraven, the regent tries to pass off Selene's accusations as a conspiracy theory. When Selene enters with the severely wounded Lycan scientist, Singe, as her prisoner, Singe admits that Lycans had been experimenting to combine the bloodlines of the two species with the Corvinus Strain. The Lycans were trying to create a Vampire-Lycan hybrid which would be more powerful than either race.
Meanwhile, in the lycan lair, where Michael is being held captive, he learns (partially through memories he inherited upon being bitten, and partially through being told) how the war began. Lucian married a vampire, whom Viktor killed to prevent the mingling of the two bloodlines. Lucian sought revenge, leading to war.
After Singe reveals Kraven's treachery, Kraven flees, and Viktor kills Singe. Viktor instructs Selene to kill Michael, and the coven sends a team of Death Dealers to attack the Lycan lair. In the ensuing battle, many of the vampires and Lycans are killed, and even the Lycan leader Lucian, is severely wounded. Before dying, Lucian urges Selene to bite Michael, so that his blood will have both Lycan and vampire strains. In the confrontation, Selene learns that it was Viktor who killed her entire family, and not the Lycans. Michael, who has been bitten by both a Lycan and a Vampire, turns into a werewolf, and attacks Viktor. Despite Michael's hybrid strength, he is no match for the powerful elder, and so Selene dispatches Viktor with a sword. Selene flees from this scene of carnage with Michael, realizing that by killing Viktor, she too will become targeted by the vampires.
As Singe's blood seeps through the trapdoor of the sarcophagus of the remaining elder, Marcus, he begins to revive.
|Kate Beckinsale||Selene: A vampire specializing in assassinations, known as a "Death Dealer"|
|Scott Speedman||Michael Corvin: A medical student who is unaware that he carries the rare Corvinus Strain in his blood|
|Michael Sheen||Lucian: The leader of the Lycans, an ancient clan of werewolves|
|Bill Nighy||Viktor: A powerful vampire elder who is awakened from his crypt by Selene|
|Shane Brolly||Kraven: A vampire appointed as interim leader (regent) of the vampire coven during Viktor's hibernation|
|Erwin Leder||Singe: A Lycan scientist who is experimenting with the Corvinus Strain|
|Sophia Myles||Erika: An attractive, blond vampire woman who is enamoured with Kraven|
|Robbie Gee||Kahn: A weapons expert, gunsmith, and chief "Death Dealer"|
|Wentworth Miller||Dr. Adam Lockwood, a medical intern who works with Michael at a hospital|
|Kevin Grevioux||Raze: A powerful black Lycan who acts as Lucian's lieutenant|
|Zita Görög||Amelia: The only female vampire elder|
|Scott McElroy||Soren : A vampire henchman who acts as Kraven's lieutenant|
|Sándor Bolla||Rigel: A male "Death Dealer" who is killed during a shootout in a subway|
|Hank Amos||NathanielThe second "Death Dealer" who was tracking the Lycans in the subway|