After a fight with two nightmarish creatures in a dark alley, Billy learns that his best friend has been infected by the viral DNA of one of the creatures. If his friend doesn't get help soon, he will become a monster himself. The only cure lies with an ancient order of warrior monks half a world away.

But finding a cure for his friend is only the beginning of Billy's problems. A war is brewing between these creatures from the darkest depths of the earth and the surface world, and Billy is the only one who may be able to stop it. Now, he must make a difficult decision - save his best friend's life or risk all of their lives to prevent an apocalyptic war that would destroy everything, both above and below.