American PI Elias Grimm has just accepted the case of a lifetime: billionaire Baron McPherson's son has died, and his father is sure it's murder. McPherson's offer is worth enough that Elias can finally get Uncle Sam and his ex-wife off his back. Elias travels to Japan, where he finds ancient grudges, the mystical power of a deity, and the equally mysterious Madison Suou, who might hold all the answers Elias needs.

Elias soon learns that the billionaire's son was only one of many victims, and he knows he's ill-equipped to handle a serial killer. Especially one who kills in a manner that can't be explained by modern medicine or science. But the money’s too good to back out, and so is Madison.