Plot
In 1933, dhampir Rayne is recruited by the Brimstone Society, a secret society that monitors and combats supernatural threats to humanity. For her first mission as a member of Brimstone, Rayne is deployed to the town of Mortton, Louisiana, to investigate reports of a plague that is transforming local residents into zombie-like mutants. She is accompanied by Mynce, a fellow dhampir and Rayne's mentor.
In Mortton, Rayne finds the town infested by spider-like monsters called Maraisreq, one of which devours and apparently kills Mynce. Rayne learns that the Maraisreq were summoned as part of a Voodoo ritual. After killing the "queen" Maraisreq, Rayne finds a strange glowing rib in its corpse; when she touches it, the rib immediately inserts itself into her own torso. Before she can recover from the shock, Rayne is attacked by a man in a Nazi uniform who forcibly removes the rib from her body and leaves her for dead, although she survives.
Five years later, in 1938, Brimstone sends Rayne to Argentina to perform reconnaissance at a mining facility where the Nazis are rumored to be searching for a mystical relic of great power. Rayne is provided with a target list of high-ranking Nazi officers to assassinate, one of whom she recognizes as the man who attacked her in Louisiana; Brimstone identifies him as Jürgen Wulf, leader of the Gegengeist Gruppe (G.G.G.; literally "Anti-Ghost Group"), the Nazi counterparts of Brimstone who seek to harness occult powers with which to strengthen the Third Reich. A Thule Society high priest tells Rayne that the Nazis are searching the mine for the skull of Beliar, a legendary king of Atlantis, whom the Nazis revere as the pinnacle of Aryan superiority.
As Rayne descends into the mine, she discovers that the facility has been overrun by "Daemites," demonic parasites that take humans as hosts and serve to guard Beliar's skull. Deep within the mine, Rayne locates the crystal skull containing Beliar's eye, the true relic, which inserts itself into her head, granting her enhanced sight. One of Rayne's targets, the cyborg Mauler, boasts to her that Beliar was not an Atlantean king at all, but was in fact the original devil. Beliar was overthrown by Mephisto, who dismembered him and scattered his body parts across the world. The rib from the queen Maraisreq is one of these parts, and the eye from the mine is another, but the most powerful relic, Beliar's heart, is buried beneath Castle Gaustadt in Germany. The Nazis collapse the mine in order to destroy the Daemites, and Rayne departs for Germany to confront Wulf and prevent the G.G.G. from recovering Beliar's heart.
Unbeknownst to the Nazis, Castle Gaustadt is home to a clan of ancient, vicious vampires who, living in isolation, have evolved into ravenous predators. One of these vampires, Hedrox, manages to obtain Beliar's heart, but does not know how to access its powers. While the vampires and Nazi soldiers attack each other, Rayne fights her way into the castle, where she encounters Mynce. Mynce reveals that she faked her death in order to infiltrate the G.G.G. and has been working as a double agent for Brimstone ever since. She warns Rayne that Wulf has already absorbed several of Beliar's relics into his own body, making him virtually invincible. Shortly afterward, Wulf ambushes and murders Mynce, ripping her heart out in front of Rayne. A furious Rayne swears revenge on Wulf and follows in pursuit.
During a confrontation with Rayne and Wulf, Hedrox consumes Beliar's heart, inadvertently summoning the demon into his own body. The revived Beliar demands that Rayne and Wulf return his stolen relics, leading to a three-way fight between them. After a pitched battle, Rayne decapitates Wulf and destroys Beliar, causing him to violently implode. Although Rayne briefly appears tempted by the power of Beliar's still-beating heart, she ultimately disposes of it by kicking it down a storm drain.
The Brimstone Society are pleased by Rayne's success and note that she deserves a rest, but they caution against the growing threat posed by another, even greater evil: Rayne's vampire father.
