The rain drummed against the tin window sills, flowing briskly down the cobbled streets of the old town. Kalina, Igor and Leon were sneaking under the canvas roof of an old tenement house at 7 Dworcowa St. It was the beginning of September, the city was reviving after the summer stagnation, and they sensed that with the end of the summer holidays, an era was coming to an end. However, that afternoon, instead of talking about going back to school and matriculation, they stopped by the decayed gate leading to the forgotten courtyard. - 'Look at this,' Leon said, wiping a smudged mark on the wall with his sleeve. On the red brick, amidst the thick ivy greenery, appeared the outline of a narrow iron door - the kind no one had seen here for years, although they had walked this way hundreds of times. Kalina, usually sceptical of urban legends, came closer. - 'They were never here,' she said, measuring the rusting hinges with her gaze. - Who installs a door deep in the courtyard between the wall and the fence? Igor, the quietest of the two, gently placed his hand on the handle, as if afraid that a touch would awaken something in the courtyard that could no longer be silenced. - Perhaps it was simply a storage room? Or a passage to the neighbouring tenement? For a while, only the rain interrupted their silence. Finally, Leon, clearly excited, elaborated: - Closed? Igor pressed the handle. To their surprise, the door gave way with a slight creak, revealing darkness. Inside, it smelled of dampness and something else - maybe dust, or maybe something that shouldn't have a smell at all. - Do you want to go in? - Leon asked. In response, Kalina pulled her phone out of her backpack and switched on her torch. A streak of light cut through the darkness, revealing a narrow corridor. The walls, although covered in cobwebs and graffiti, looked as if time flowed differently here. They entered slowly, carefully, absorbing every rustle and sound of their own footsteps. The corridor meandered, leading deeper and deeper beneath the tenement. In the distance, something silvery glimmered - an oval structure, almost transparent, trembled slightly under the light. - It looks like... I don't know, like something out of quantum physics - whispered Igor, looking fascinated at the shimmering swirls in the air. Kalina held her breath. Her heart was pounding like a hammer. - After all, it's impossible. After all, it's ... Leon did not finish. The oval portal flashed with blinding light and the floor trembled beneath their feet. At the same moment, there was a deafening slam of the door closing behind their backs. They were left alone in the corridor, with the light of the portal before them and the knowledge that it would no longer be possible to return along the same path....