They are carelessly happy and looking forward to celebrating passing their school-leaving exam on a warm summer evening at the castle high above the town: Karla and Lucie, two inseparable friends, and their ex-classmates. Everything is ready: music, wine and burning torches casting dramatic shadows on the old walls. The party could begin – were it not for a man dressed in a black, bat-like cloak standing on a castle wall and looking as if he might jump into the abyss at any moment. Lucie, never at a loss for words, breaks the tense silence and persuades the young man to come down from the wall. He turns out to be one of the Disciples of Satan who have been terrorising the area for some time. Lucie is fascinated by the sinister young man, and Karla, knowing Lucie's weakness for weird things, fears for her friend's spiritual welfare.