The Continental Op investigates a diamond theft at a laboratory, which leads him into the troubled world of the Leggett family and a young woman, Gabrielle, who believes her family is cursed. Along the way he meets cult leaders, spiritual fads and a series of puzzling deaths in southern California. The Op remains a skeptical, practical observer as the mystery widens across several parts. The novel is more sprawling and strange than Hammett's others, and it explores belief, fear and the pull of superstition.