The old dentist's surgery on Florianska Street had long aroused awe and fascination among the townspeople. For Julia, Olek and Iga, however, it was a challenge - a place where something was waiting to be discovered. One June evening, they made a decision: they would go in there after dark. It was said that not only machines and tools were left inside, but also something that even the bravest dentists feared - the legendary Enamel Map. Squeezing through an ajar window in the waiting room, they smelt an intense, slightly chemical smell, and their footsteps echoed through the empty corridors. Old lamps dangled from the ceiling, as if ready to fall at any moment. X-rays of unknown people hung on the walls, and underneath them were strange notes in which the words 'decay' and 'mystery' were repeated. In one of the offices, Olek found a strange indentation in the floor. He slid his fingers into it until suddenly the whole slab moved away with a quiet creak. Below them stretched a staircase leading to another world. They carefully descended and.... they froze. The room resembled a subterranean city built of huge, shining crystals resembling tooth enamel. In the middle stood a mysterious machine - it looked like a giant toothbrush that crunched quietly, as if it had just cleaned something invisible. Julia, the bravest of the two, walked closer. The inscription on the machine read: "Cleanliness is the key". Iga noticed that coloured balls resembling lozenges for breath freshening were scattered around. They decided to solve the riddle of the town, but suddenly Olek felt a sharp pain in his tooth and.... disappeared without a trace. A strange metallic laughter sounded in the air and the whole underground space flashed with a harsh light. Julia and Iga looked after each other in horror, trying to make sense of what had happened as the mysterious door slowly began to open....