Primary School No. 27 in Green Valley looked like any other: a long, white building, with a courtyard full of laughter and bustle. Asia, Tom and Lena knew every nook and cranny of this school, or at least they thought they did. One Thursday morning, all the pupils in Class 6a were talking about only one thing - the big renovation that had just started. The smell of fresh paint was everywhere and the school corridors were full of cardboard boxes and tools. Everyone walked carefully so as not to get dirty with paint or trip over a pipe. During the break, Asia began to tell the story in a whisper: - 'I saw something strange by the music room. There was... a door. One that had never been there before! - Impossible - snorted Tom. - I know every corner of this school. - Then come and see! - Lena was already ready to move. Leaning behind the pillars and dodging the renovating workers, the three friends arrived in front of the music hall. Indeed, right next to the familiar double doors, there was a new one - matt grey, without a handle, only with a small window at the very top. They looked as if they led... nowhere. - Maybe it's a storage room? - Lena wondered, putting her ear to the door. At that moment, the light in the corridor flicked on and they heard a quiet sound from behind the door, as if someone on the other side had moved slightly. Asia moved away cautiously. Suddenly, something silver flashed through the window. Tom whipped around playfully: - Maybe it's the caretaker's ghost? - But even he didn't sound as confident as usual. Before anyone had time to say a word, the door unexpectedly swung open a centimetre, creaking shrilly in the process. The three friends looked at each other, their hearts pounding like crazy. Someone whispered quietly on the other side: - Are you coming in or are you scared? It became quiet. Asia felt chills down her spine. From that moment on, a normal school day was never going to be like this again....