In the Edo period, an old lady is murdered and a hundred ryo are missing. A merchant who had borrowed money from her is suspected, sentenced and executed. In comes the man's son from out of town. This is nothing like his father and he begs the magistrate, Kazuo Hasegawa, to reopen the case and exonerate the dead man. A couple of sedan carriers think they saw a local ronin that evening.
It's a comedy mystery, and Hasegawa plays Ooka Echizen-no-kami Ooka, a real person (1677-1752), about whom many stories were told concerning his clever judgments; it's as if someone were writing a mystery novel about John Marshall. Given the reliance on stereotypes of the era -- cowardly lower classes, hot-tempered ronin, and the deus-ex-machina manner in which the whole thing is settled, I wasn't too impressed.
