Sano Ichiro, now the shogun's chamberlain and second-in-command, returns to his previous role of criminal investigator after the country's top spy, Ejima Senzaemon, drops dead on his mount during a horse race. Sano quickly finds that Senzaemon was just the latest senior official to die without warning. With the assistance of Hirata, his longtime assistant, the chamberlain uses his highly irregular sources to get on the trail of a martial-arts master using the legendary dim-mak, or touch of death.