The Rust Gate, the old townspeople said, had a character all of its own - it stubbornly refused to be demolished, although there were attempts to do so as late as the 1960s. The fort, tucked away on the outskirts, was overgrown with nettles and ivy, and the bars on the windows were a reminder of wartime. Every generation of teenagers sooner or later set foot there. Szymon, Julia and Natalia, three friends in their final year of high school, were not looking for trouble - rather challenges that give a real adrenaline rush. Simon was the brains of the operation, always familiar with maps and plans, Julia had a gift for spotting what others don't notice, and Natalia Natalia loved sound - the recorder was almost part of her body. Entering the fort, everything seemed ordinary: classic graffiti, rubble and wine bottles. But deeper down was an iron trapdoor, strewn with rubble. Julia urged the boys to try to lift it. Under the trapdoor they found a concrete shaft with shards of glass around the edges. They climbed down the slippery ladder; there, in the cool twilight, awaited a room that was not on any plans. In the centre - a metal ring embedded in the ground, decorated with incomprehensible symbols. Next to it lay an old, mould-covered book. Natalia switched on the torch on her phone, and the light fell on the ring. When Julia touched one of the engraved signs, a strange sound pierced the air, low and throbbing, as if a deafening rhythm was coming from underneath. Simon - always sceptical, this time trembled. - Did you see that? - whispered Julia, withdrawing her hand. The ring flared with a pale blue glow, and the air thickened. The book suddenly shook on the floor, opening on a page written in a language they did not recognise. A lump of dust blew off the ceiling, falling onto the metal. At the same moment, Natalia heard a sound through her headphones that none of their devices registered - something that resembled a time-reversed heartbeat. The light grew more and more intense. At the opposite end of the room, something that resembled a water vortex - only that it was embedded in the air - began to flicker. Simon took a step towards the phenomenon and felt the ground beneath his feet vibrate. They heard a quiet rustling. Someone - or something - must have moved on the other side of the portal....