When the clock on the town hall struck midnight and the town fell asleep plunged into a thick fog, Lena, Michael and Igor were already standing under the old bridge. They stared into the darkness, trying to see more than just the outlines of the rusty railings and the glistening narrow river that flowed beneath. Rumours had been circulating around the school for weeks. It was said that someone or something was appearing under the bridge - that whispers, metallic clattering or quiet laughter could be heard. No one had the courage to check it out for themselves, but Lena didn't believe in ghosts. She bet Igor that nothing would happen. Michal, decidedly less convinced by the whole idea, tried to catch up with them on his bike with a torch hung around his neck. For a while, only the sound of the river and the distant, sleepy barking of a dog cut through the silence. Suddenly Lena leaned over the railing. "Listen! You can hear it again!" - she whispered. Igor looked at her suspiciously, but immediately heard it himself - as if someone was quietly singing just under the bridge. The melody was strange, as if familiar, and yet.... alien. Michal squeezed the torch and moved slowly towards the descent to the shore. As soon as they went under the bridge, the silence exploded with the echo of a clatter - something or someone was sneaking past the pillar. Michael's torch danced across the wet stones, illuminating a narrow tunnel neither of them had heard of before. Dampness and chill beat from the tunnel. "It's impossible, there's never been a tunnel here," whispered Igor with his eyes wide open. The mood between them thickened like a fog. A faint light shimmered from the darkness of the tunnel, as if someone was waiting on the other side. The melody fell silent, but the echo of their footsteps seemed to bounce off the invisible walls more and more strongly. Lena took the first step towards the mysterious entrance, turning to the boys, "Do you want to see what's here, or are we going back?" At the same moment, a long, drawn-out whisper sounded from inside the tunnel - so clear that it made everyone's stomach clench. All three froze, staring into the darkness, from which someone or something began to slowly emerge to meet them....