The evening sky was covered with heavy, dark blue clouds when the group of friends - Lena, Kuba and Maks - arrived in front of the abandoned factory on Hutnicza Street. The place had been a silent witness to their childhood for years, but this time the atmosphere was different. Instead of carefree play with a pushed ball, there was a shiver of anxiety caused by rumours of recent strange phenomena - a sudden glow, unexpected sounds, disappearing cats. Lena led the way. She was curious, adventurous, sometimes all too much so - which often got her into trouble. Kuba cheered on all the crazy ideas, although he himself would be happiest reading books at home. Maks, perpetually with a camera around his neck, documented their every craziness. This time it was Lena who suggested exploring an abandoned building. - Do you know what they say about old factories? - Lena began, looking around the dark windows. - That they hide things that philosophers never dreamed of. Kuba rolled his eyes, but followed her inside. The echoes of their footsteps reverberated off the concrete walls. The smell of rust and dust was in the air. After a while, they came across a strange, shiny gate mounted inside one of the halls. It stood out for its modernity amidst the crumbling walls. It hadn't been here when they last toured the factory. The glass arch was covered with pulsating patterns that changed, as if reacting to their presence. Maks automatically picked up his camera and took a picture. As the flash reflected in the surface of the gate, something happened: for a split second, they saw an alien landscape painted in the sheet of glass - an unfamiliar city full of lights, hovering buildings and swirling, luminous spheres. Then the image disappeared and the room around them ceased to exist for a moment. - Hey, did you see that? - whispered Kuba, extending his hand towards the archway. The glass surface trembled. They could feel the tension building up around them - as if the air was thickening. A metallic clatter sounded behind them. They turned abruptly, but saw no one. When they looked at the gate again, they noticed that one of the swirling patterns had changed into a door-like shape. At the same moment, light from the archway spilled across the hall, and Lena realised that her shadow on the floor had suddenly lengthened and reached all the way to the edge of the gate. She felt that something - or someone - on the other side was watching them too. They took a step forward, absorbed by the mesmerising light of the glass gate - not knowing what was waiting on the other side, or whether they would manage to return.