That day, Lena walked home from school more slowly than usual. The rain that had been hanging in the air since the morning had finally started to fall, so she wrapped herself tighter with her scarf. She had just passed an antique shop on the corner of the street when she noticed something strange: a man in a long coat was looking at her through the glass, holding a small silver key in his hand. He smiled mysteriously and nodded, as if he was waiting just for her. Lena felt a shudder, but curiosity won out. She stepped inside and the bell hung a quiet, melancholic sound in the air. The interior smelled of dust and old leather, and the shelves were stacked with books with titles she had never seen in any bookshop. A man came closer, his dark eyes glinting in the semi-darkness. - 'This key is for you, Lena,' he said, as if it were obvious. - It will only open one door. You will find it in the house, but don't look for it simply. Look carefully. Without understanding much, she took the key. When she returned to the flat, she unwrapped it surreptitiously. It was heavy, cool and decorated with a silvery pattern resembling a spider web. Lena walked around the house for a long time until her gaze finally fell on the old mirror in the hall. Suddenly the silver key trembled in her hand. She lifted it higher, and its reflection in the mirror shimmered like a rainbow in a drop of water. With hesitation, she touched the sheet of glass with the key. It vibrated, and the surface of the mirror began to ripple. Lena walked over to the other side. Immediately she felt that she was somewhere else. Everything around her was familiar, but... more colourful, as if someone had soaked the world with magic paint. Corridors full of doors of different sizes stretched around her, and quiet laughter and whispers came from far away. A wooden sign hung above the entrance: 'School on the Other Side of the Mirror'. Before she could ask herself if she was dreaming, she suddenly heard a voice behind her: - You're late for your magic lesson, Lena! - called out a girl with green hair, waving to her from the end of the corridor. Lena moved towards her, but suddenly the doors around her began to open abruptly. Mist gushed from one, luminous butterflies spilled out of another, and in the last stood a tall figure in a cloak with silver runes. Everything began to swirl, and Lena felt that her greatest adventure was about to begin. What lay behind the door and why had the key chosen her?