 The start of this horror story sees Renata, a journalism-school expellee making her living as a clerk, take a new roommate, an Argentinean girl Tess who came to Prague to study architecture. It could be an ordinary youngster story, had their friend David not found plans of inaccessible dungeons under the Lesser Town in a book Tess had bought. The friends meet Dr. Sima, a peculiar doctor, who may just be kidding them all, having the situation as a means to get close to Renata and Tess, but might as well know things about the underground no one else can think of.