As the thick, autumnal fog chokes the capital, within the fire-lit lounge of London's notorious Brimstone Club a bizarre tale is being spun for Inspector Bencolin and his friend Jeff Marle. A member of the club has been sent a model of a tiny gallows, and the word is that the folkloric hangman Jack Ketch has been stalking the streets for victims by night. The threat of this supposed bogeyman becomes thrillingly real when that same night Bencolin and Marle are almost run down by a limousine with a corpse behind the wheel. When an ominous message claims the car's passenger has been taken to the gallows at Ruination Street for hanging, the detective and his associate venture into the night to discover the truth behind the terrifying Ketch and a street which cannot be found on any map.