Edo, 1703. A destructive earthquake has reduced neighbourhoods and government buildings to rubble, leaving the shogun’s regime vulnerable to disorder. Beneath a collapsed house, Sano finds two young sisters whose deaths were caused by poisoned incense rather than the disaster.
Their powerful father threatens political retaliation unless Sano finds the killer. Reiko assists while Hirata’s unexplained absences weaken the household, and enemies use the emergency to prepare a challenge to the government. The murder investigation unfolds amid famine, displacement and unstable authority, where every aftershock intensifies the struggle over who will control the recovery.