The rich and influential feudal lord Mr. Inaba is killed at night in his home in the very center of Edo. There are no witnesses, and a bloody stain in the shape of an origami butterfly was found next to the body. Who needed the death of Mr. Inaba?.. Judge Ooka, his stepson Shokei and samurai Tatsuno set off on the trail of the criminals. But the villain, as often happens, turns out to be very close.