At night, when the light of the lanterns cut off only pale spots on the wet cobblestones, Lena, Kuba and Marcin met on an old bridge on the outskirts of the city. The place, shrouded in ancient legends and whispers of passers-by, had already attracted them for several weeks. Especially now that the river had subsided and pieces of clay bank were exposed under the bridge. They sat for a while on a weathered wall, sharing a can of cheap coffee from a vending machine and talking about everything and nothing. The city was sleeping peacefully, with only the sound of the last tram coming from the distance. Then Lena noticed something unusual. In the wall under the bridge, which had always seemed uniform and inaccessible, there appeared a crack the width of a hand. For a moment it seemed to her that something was shining inside. - Can you see it? - She whispered, pointing to the spot with her finger. The guys stopped talking and gazed into the darkness under the span. The crack was indeed there - almost invisible in the daytime, but now it shone pale like broken glass. They stepped carefully down the slippery slope, soiling their shoes in the mud and feeling the chill beating off the old stone. Lena pressed her hand to the crevice. The stones began to vibrate strangely under her fingers. She accidentally pressed a fragment with an engraved spiral, and then the whole wall trembled and slowly, with a groan of steel and a rustling echo, moved away, revealing a low tunnel in which dark twilight reigned. The smell of earth and wet brick hit them in the faces. Cuba took the first step inside, casting the light of his torch on the walls covered in glistening crystals. Marcin pulled down his hood and looked at Lena with an uncertain look on his face, but she just shrugged her shoulders and walked in behind Kuba. The door in the wall closed silently behind them, leaving the outside world somewhere far away, behind a thick wall. The corridor turned slightly to the right and descended lower and lower, the air growing warmer, almost electric. Somewhere further down, sounds could be heard - it was impossible to recognise them, as they resembled both a hum and quiet laughter. At one point, Lena tripped over something hard. Kuba stopped and raised his torch. In front of them, almost at the end of the tunnel, an arched portal was emerging. It was all covered in pulsating light, decorated with strange symbols and hanging crystals. A hazy glow was pouring through the centre of the portal, as if someone had poured the light of a full moon into it. The three friends looked at each other in silence for a moment. It only took one step to see what was next. At the same moment, the portal shook slightly, and a long, drawn-out cry, reminiscent of a voice but distorted, out of this world, rang out from its centre....