Lena never imagined that the library at her school hid any secret. After all, she knew it by heart - from the creaking parquet floor, to the heavy bookcases and old Mrs Brigid, always sitting at the entrance. However, that Friday afternoon, as she waited for her friend after lessons, everything changed. The silence of the reading room was broken by a quiet clatter from behind the bookcases. Lena glanced in the direction from which the sound was coming - there was a bookshelf she had never seen before. It looked older than the rest of the furniture, covered in cobwebs and dust, as if no one had moved it for years. - 'Mrs Brigid, and what is that shelf in the corner?' - She asked, feeling her heart beating faster. The elderly librarian smiled mysteriously and just said: - Not everything in this library is for reading, Lena. As soon as Brigid returned to her desk, Lena moved towards the shelf. She was surprised because, standing close, she felt a cool breeze. She moved a few books - suddenly one of them swung out on its own, and behind it appeared a a door. It was narrow, wooden and had an ornate silver key stuck in the lock. At that moment Kuba, her friend, entered. - What are you doing? - He asked, noticing Lena's fascinated expression. - Look! - She whispered and drew him towards the discovery. They both looked at each other still uncertainly, but curiosity was stronger than fear. With hesitation, Lena turned the key. The door creaked and opened slowly, revealing a narrow, dark corridor. Luminous dust floated inside, and the walls shone as if they were made of a a moving mosaic of images and words. - Shall we go in? - Kuba looked at Lena in agreement. Lena nodded. As soon as they crossed the threshold, the door closed silently behind them. The light from their phones bounced off the walls, creating ever-changing scenes: dragons, castles, cities floating in the air. Suddenly, a quiet voice came from the depths of the corridor: - Have you come to find me...? Lena looked at Kuba. Her heart was beating like crazy. She was already about to reply when a blurry silhouette emerged from behind a corner, and the images on the walls began to swirl faster and faster....