The old vaults beneath the abandoned school were the only place to escape the hustle and bustle of everyday life. Michal, a seventeen-year-old lover of chemistry and logic puzzles, knew them like the back of his hand. But that evening, when they were standing there with their friends - Susie, who was always asking about the old days, and Christopher, a computer enthusiast - something was different. The cool light of torches cut through the twilight, sweeping over peeling walls and ominous shadows. Michal ran his fingers over a brick on which someone had carved strange symbols years ago. Zuza squinted her eyes. "It's not just graffiti. Look, there's a mechanism here!" Krzyś took a penknife out of his pocket and together they began to scrape away the layer of dust. Hidden under the dirt was a small button. Michal hesitantly pressed it, and then.... The entire wall trembled and moved away, revealing a narrow corridor leading into darkness. Fatigue and anxiety gave way to excitement - neither of them could resist the temptation to learn the secret. They passed through the aisled passage and the door closed behind them with a deafening clatter. The interior lit up with a pulsating, bluish light, and images began to swirl around them: scenes from bygone eras, fragments of old newspapers and photographs of people they had never seen before. After a while, they found themselves in a large room with a centre in which a bizarre clock was stuck - its hands moving in opposite directions. "It's... a time machine?" - whispered Zuza. Before they had time to grasp what was really happening, the world around them began to distort. In an instant they were standing in the middle of a cobbled street, surrounded by strangers in centuries-old costumes. Shouting, confusion and the sound of police whistles - suddenly Michael felt something heavy in his pocket. He took out an old-fashioned key with the same symbols engraved on it as on the wall in the basement. Someone in the crowd pointed a finger at him. "It's them! Predicted by the Prophecy!" The friends looked at each other in horror - would they be able to return to their own time? Would their presence in the past change the fate of the world?