The clock in the corridor chimed twenty o'clock as Marta, Adam and Lena crept through the creaky door into the oldest part of the school library. The place had been locked up for years, and legends circulated about its past. Brave though they were with a shudder of anxiety, they left their everyday lives behind - lectures, sessions, coffee and nerves - and entered a world of paper shadows and the smell of old volumes. "It's darker than I thought," Lena whispered, turning on the torch on her phone. The light revealed rows of dusty shelves and a table on which yellowed pages were piled. Adam picked up one of them. "Check this out... I think it's a diary. It looks... very old." Martha opened the book carefully. The letters flowed across the pages like shadows on a wall. As they read aloud the first words, they felt the air thicken and the library around them seemed to absorb every sound. Suddenly, there was a rustling sound from deep within the bookcases - as if someone was moving books on the shelves. Lena looked into the darkness. "It wasn't the wind," she said quietly. A silhouette emerged from the gloom, barely visible in the faint light of the torch. "Who's here?" spoke up Adam, his voice trembling. Silence. But then there was a whisper, very quiet, as if coming from behind a wall: "You shouldn't be here..." The three friends froze, their hearts beating like crazy. Martha tightened her hands on the thick volume. Suddenly, a mysterious, flickering light flashed in the corner of the room, and the hidden door behind the bookcase began to slowly swing open....