At night, the Old Town looked very different from the daytime: the cobbled streets glistened with moisture after the rain, and the street lamps cast long, fuzzy shadows on the walls of the townhouses. David, Lena and Kacper, three friends from the neighbourhood, gathered in the market square that evening to finally try to solve the biggest mystery of the neighbourhood. For weeks there had been rumours of a mysterious tunnel hidden somewhere under the foundations of the town hall. It was said to have once been used by smugglers, but then its existence was forgotten. Each of the friends had their own reason for taking the risk of this expedition. David had always dreamt of adventure and the feeling of being part of something extraordinary. Lena had a knack for solving puzzles and could never let go of mysteries. Kacper, on the other hand, although seemingly cautious, was eager to break the daily routine. They cautiously made their way to the wall of the town hall, following clues found in his great-grandfather David's old diary. According to the notes, the entrance to the tunnel was behind a stone gutter, hidden under a clump of ferns. After a few minutes of searching, Lena sensed a cold blast beating from between the stones. They pushed back the gutter and to their eyes appeared a narrow, dark opening leading deep into the ground. With a beating heart, they slipped inside. Torches illuminated the damp walls with mysterious symbols carved on them. The labyrinth was much larger than they had guessed: they passed side corridors leading nowhere, old, rusty doors and traces of torches once set up. When they reached a fork, they noticed a fresh new sign on the wall - an arrow and some strange writing whose meaning they could not decipher. Before they could decide which way to go, somewhere around the bend they heard a quiet murmur, as if someone else was in the tunnel. Lena's torchlight shook and the echo of footsteps bounced off the damp walls. The friends looked at each other - they were no longer sure if it was them following the mystery, or if someone was just following them....