It all started one August evening when Michal, Lena, Igor and Paula were cycling back through the old part of the city. The sun was barely breaking through the dark clouds, and it had become almost completely grey on Strzelnicza. Passing an abandoned, overgrown house at number 17, Michal suddenly braked. ‘Look!’ he whispered, pointing to an upstairs window. A faint greenish flash ran through the glass. It looked as if someone was waving a torch underwater. Lena, who has always had a talent for sensing unusual situations, immediately stopped. ‘After all, no one has lived here for years! Everyone says this house is haunted, remember?’ Igor rolled his eyes, even though his hair, under his hat, stood on end. Paula was the bravest of them all. ‘Maybe someone just broke in there. Or it could be some kind of joke. Shall we go and check?’ The others were in no hurry, but curiosity was stronger than fear. They jumped over the rusty gate, then trudged through the tall grass until they stood at the door. A quiet rustling sound came from inside the house, as if someone was moving across the creaky floor. ‘Did you hear that?’ whispered Michal, squeezing the handlebars of his bicycle so hard that his fingers turned white. Igor slowly pulled out his phone, switching on his torch. The door was ajar – just enough for them to see a patch of dark corridor flooded with pale green light. Paula, usually confident, stopped just short of the threshold this time. ‘Someone in there?’ she called, loud enough to make the cobweb in the corner of the doorway tremble. She was answered by silence, even deeper than before. Suddenly, there was the sound of heavy footsteps in the depths of the house. The green light began to vibrate and turn purple. At the same moment, they heard the crash of breaking glass and a broken whisper: ‘You must not enter here…’ Everyone froze, staring into the illuminated corridor. Something – or someone – was just coming towards them…