The damp air seemed to thicken with each step. Anna, Kuba and Marta walked quietly along the cobbled streets of the Old Town, where the lights of the street lamps blurred in the puddles after the evening rain. It was almost midnight, but instead of heading home, they were drawn to something else - an old map that Anna had rummaged through among her family heirlooms. The yellowing paper showed a line leading all the way to the underground tunnels under the market square and a strange annotation: 'Entrance behind the fountain, only on solstice night'. On this solstice night, intrigued, they slipped out, sneaking between empty benches and sleeping pigeons. When they reached the fountain, Martha found a metal trapdoor hidden under a rusted grate. Cuba, always the first to act, levered the grating open with a penknife. They went carefully down, underground, where they could feel the cold and the silent echo of the footsteps of long-forgotten people. The underground proved to be a labyrinth of walled passages and damp walls. Torches nervously swept the shadows. On one wall, Anna spotted a recently painted symbol: three intertwined spirals in red paint. "What is that?" - whispered Marta. From the depths of the tunnel came a quiet sound, reminiscent of a whisper. Someone or something was with them under the city. The friends stepped back, but behind them they heard the slamming of a grating closing. Martha was trembling with anxiety. An unfamiliar light flashed from around the bend of the tunnel....