Sotaro walks into the Dark like he's done it a hundred times before, and the movie never explains what he finds there. The steampunk maze doesn't follow logic, it follows mood, shadow, the feeling that answers exist in places that don't quite make sense spatially or morally. You leave without resolution because the investigation itself is the point, not the answers, and that gutsy refusal to land the story separates this from every other detective noir you've seen.

The Ootsuji Detective Agency is short on work, so Sotaro and his young sidekick Saki accept whatever comes their way, however risky. During the city's festival season, a string of mysterious disappearances unfolds out of public view. A newspaperman hires Sotaro to look into it and suggests the answers may be found in the Dark, a lawless underground labyrinth beneath the city. Sotaro passes the job to Saki, then comes to regret it when the kid goes missing too. Now he has to go down into the Dark himself, where he faces its shady inhabitants, among them the Laughing Masks gang and a renegade police unit operating the armored train Demon 463 under its commander, Tanne. The film is a fantasy mystery.