Father O'Sullivan is a Catholic priest who has lost his faith. He can't forget the nun with whom he once had an affair (and a son). He serves as a guide for American tourists who are innocently looking for a tour of Aztec ruins. O'Sullivan meets archaeological student Cal, who turns out to be the brains of the bunch. New Agers Wilbur and Clarisse Lemming are silly but earnest. Runaway Laurie is trouble, and prone to gossip. Tourists Dozois and Frost want to have fun in Mexico. O'Sullivan is astonished when his love, Tessie, also boards the bus with her (their) bratty son, Ivan. The tourists find fantasy and evil in Mexico. Is it black magic? An evil doctor plans an apotheosis for himself: one that will culminate in his incarnation as the Death God. What he needs is the hearts of sacrificial children.