Set in 1920s New York City, the novel depicts the elderly Harlem houngan PaPa LaBas and his companion Black Herman racing against the Wallflower Order, an international conspiracy dedicated to monotheism and control, as they attempt to root out the cause of and deal with the "Jes Grew" virus, a personification of ragtime, jazz, polytheism, and freedom. The Wallflower Order is said to work in concert with a still-existent Knights Templar Order to prevent people from dancing, to end the dance crazes spreading among black people. The virus is spread by certain black artists, referred to in the novel as "Jes Grew Carriers" or "J.G.C.s."