Sano Ichiro, Most Honorable Investigator for the shogun in 17th-century Japan (The Samurai's Wife, 2000, etc.), tackles the murder of the police commander, Oyama Jushin, and an unidentified woman and child whose burned bodies have been found in a charred building on the grounds of the Black Lotus Temple, a new and influential Buddhist sect. Sano has no clues and only one witness: Haru, an orphaned girl under Black Lotus care. Unfortunately, Haru, battered and apparently traumatized, won't speak. Sano asks his wife Reiko, his partner in other cases, to question her. Sidelined by their infant son, Reiko welcomes the opportunity to do some detective work. But the rapport she establishes with Haru threatens to ruin Sano's career and tear their marriage apart. When evidence implicates Haru in the murders, indicating that she is a habitual liar and arsonist, the shogun and his advisors pressure Sano to arrest her and close the case. Believing Haru innocent, Reiko insists that the Black Lotus and its charismatic leader Anraku, his disreputable abbess Junketsu-in, and his deadly head of security Kumashiro are behind these murders and more. Working at cross-purposes, Reiko and Sano put everything they hold dear at risk.
In a final confrontation that makes Waco look like a throwback to the shogunate, Haru, the Ichiro family, and the Black Lotus Temple finally show their true colors. Honor and spiritual emptiness have a suspiciously contemporary feel in a mystery that can't decide which is more dangerous: love or the coming apocalypse.