The rain rumbled against the rusty sheet metal of the roof, and a thick fog spread around the sanatorium, dampening the torchlight. Igor looked at Julia, who held the map with a trembling hand. David walked first, pounding out a rhythm on the concrete steps with his shoes. - 'I told you not to go this way,' whispered Julia, trying not to look into the dark windows of the building. Olive, always sceptical, sped over to see the plaque on the gate. In rusty letters it could barely be read: SANATORIUM CLOSED SINCE 1979. There was silence all around, although every now and then a single bark of a dog or the crackle of a branch breaking under the weight of the wind could be heard in the distance. The friends crossed the threshold of the main entrance. It was even darker inside, and the air smelled of dust and wet earth. Igor switched on the night mode on his camera, ready to capture any anomaly. - 'I can't believe we're doing this,' muttered David, but he stubbornly walked on, pressing his rucksack to his chest. The corridor was splitting. To the left it resembled a tunnel, and to the right stretched a series of doors to boarded-up rooms. Footsteps echoed in the silence, though none of them moved. - Did you hear that? - sighed Olive, suddenly pale. At the same moment, a shadow ran out from behind one of the doors, cutting through the torchlight beam. Someone - or something - flashed past so quickly that only Igor managed to catch the silhouette in the camera frame. Everyone froze in stillness, staring at the camera display. The screen clearly showed a stranger in a white lab coat, with his gaze directed straight into the lens. Above him, on the wall, was the inscription: "DON'T LOOK BACK". Behind their backs, they heard the creak of a door and heavy footsteps getting closer and closer....