Returning to his native Haiti (born in Port-au-Prince) after 12 years (originally nearly 20) of education and practice as an accredited psychologist in the United States, Jericho Drumm discovers that his twin brother, Daniel Drumm, the local "houngan", is dying, a victim of a voodoo sorcerer who claims to be possessed by the spirit of the serpent-god Damballah, based on the Loa Damballa. Just before he dies, Daniel makes his brother vow to visit Daniel's mentor, Papa Jambo. Jericho does, and becomes Jambo's student. After studying under the aged houngan for several weeks, Jericho gains a greater mastery of voodoo practices than his own brother, becoming a houngan in his own right. Papa Jambo then performs a rite that summons Daniel's spirit from the dead and joins it with Jericho's own. Having fashioned a worthy successor, Papa Jambo dies.