The old Industrial Works on the outskirts of the city was a place everyone had heard of, but no one dared venture there after dark. A six-storey edifice, windows broken, walls overgrown with ivy, creaking doors hanging on rusty hinges - it looked like a set from a horror film. The neighbourhood kids, including the ever-inquisitive Lena, the prankster Bartek, the serious Olek and the mysterious Hania, couldn't resist the temptation to see what was really hiding inside. It was late Friday evening when, armed with torches, backpacks of snacks and warm sweatshirts, they crossed the hole in the fence leading to the site. There was a smell of damp and rust in the air, and the night's silence was broken only by the hooting of owls and the rustling of leaves blown by the wind. - Well, Lena, where now? - asked Bartek, twirling his torch and trying not to show fear. - 'Let's go into the main hall first,' replied Lena, taking a confident step towards the large metal door. After a while, everyone was already standing inside. Their lights illuminated the space full of overturned machines, old, rusty tools and scattered papers. Suddenly, Olek stopped. - Did you hear that? - he whispered. Everyone fell silent. There was indeed a rhythmic sound coming from the depths of the hall, as if someone was slowly tapping something against metal. - It must be the wind... - Hania tried to joke, but you could hear from her voice that she herself did not believe this explanation. They decided to move on. They crossed the large production hall and climbed the stairs leading to the first floor. Every step underfoot sounded louder than it should have. The higher they climbed, the stronger the impression that someone - or something - was watching them from dark corners. On the second floor, the door to one of the offices was ajar. Bartek carefully pushed it open. Inside, in the light of torches, they saw an old desk, an armoured cupboard and a lot of dusty documents. Lena suddenly noticed something - someone had scrawled an intricate pattern on the wall in chalk, winding across the entire surface. - What is that? - She asked fascinated. Before anyone could answer, they heard a sudden crack in the corridor. Torches reflexively pointed towards the door. A shadow rolled down the corridor - it definitely did not resemble any animal. For a split second they could have sworn they saw a man in old factory clothes disappear behind a grapevine. - He left no trace... - whispered Olek, peering into the corridor. Suddenly, the light of all the torches began to flash, and the same rhythmic sound sounded again from the depths of the corridor, this time louder, more emphatic. The friends looked at each other, and their hearts began to beat like crazy.... Then the office door closed of its own accord with a bang, and the room fell into absolute darkness.