Growing up in an abusive home during the waning days of the Cold War, young Mark Arsenault has only two steadfast companions. One is a flickering apparition that appears only near the borders of sleep, whispering riddles about an apocalyptic future. The other is a bestial, inhuman entity looking out at the world through Mark's own eyes.

As he comes of age in a world of moon shots and atom smashers, Mark learns his companions are far stranger than he could have dared guess. Their fates are inextricably entangled not only with his own, but with that of reality itself. Pursued by shadowy government agents and police, Mark must risk all to understand his true nature, to save the woman he loves, and to prevent a cosmological catastrophe. To do so, he must become the thing he has always feared most, a creature of Norse myth too terrifying to unleash in this world.