Night city. Fog. Passersby shy away from the metal monster - a steam locomotive created in the workshops of the gnomes. Hanging inside it, like a pea in a dry pod, is Fairy Green, an elf and police inspector for the kingdom of Aranya. The fairies were called to determine the cause of death of Lord Arthur Bentinck, whose last words were "the mottled lizard." Inspector Green found traces of the killer immediately. It turned out to be a moss snake, or more precisely, a rare variety of it, once bred by elves. But such “variegated lizards” do not appear in the houses of lords on their own. So someone benefits from the death of young Sir Arthur? Fairy was ready to find out, but Colonel Card, commander of the Night Guard, which is notorious in Arane, intervened in the investigation. However, Inspector Green is not one of those who can be intimidated by special powers...