Kagetani Kantaro, a magnate in the drug trade, mysteriously dies in the courtyard of his own mansion. Though publicly ruled as suicide by aconite (wolfsbane) poisoning, Kantaro's nephew Yoshiaki suspects foul play, thus hiring his old acquaintance Todo Ryunosuke to investigate. The PI goes undercover as a butler, and then as a novelist, to get to the bottom of the case. What truth awaits him at the Kagetani family's manor?