An encounter with a moth can mean pleasure or death.
September 1489. Mojmír Mráz of Žezlice, the Commissioner of the Moravian Provincial Court, arrives at the castle of an old friend to investigate the death of his granddaughter. The girl was lost among the wandering comedians, to whom she fled before her forced marriage - but she could not escape her sad fate.
The clues lead to a remote town in the middle of the Moravian forests, where a series of strange murders are currently terrifying the peaceful citizens. The story goes that twelve years ago, a fairy called the Night Butterfly appeared in the area and meeting her meant pleasure or death. Now it seems that the spectre has been summoned again, and the old fear takes on a new form.
However, Mojmir does not believe that the murders are the work of an evil being and a just retribution for lust and avarice. He sets out to find a flesh-and-blood killer whose dark intentions, hidden behind the attacks of an incorporeal fairy, are gradually coming to light.