Olive had always thought their block of flats was the most ordinary in the world - concrete grey walls, long corridors, a creaking lift and a wide staircase leading to the floor. However, it had seemed to her for some time that something had changed. At first she blamed it on her lush imagination and love of adventure books, but one morning she wasn't so sure anymore. It all started with a drawer. Or, to be more precise, from a wooden shoebox that stood under the stairs, right at the entrance to the flat. She had walked past it hundreds of times without paying any attention to it. It was simply a cupboard, slightly dingy, occasionally creaking, filled with Olive's sporty trainers and her mum's tidy slippers. However, that Friday she felt a strong urge to look in it. It was raining on the way home from school. Her socks were soaked up to her ankles and her schoolbag seemed twice as heavy. She turned the key in the lock and was greeted in the flat by the smell of cocoa and her mother's favourite song on the radio. She quickly slipped off her wet shoes and - without knowing why - reached into the cupboard. Inside, to the left, something shone. After all, she had only left her grey trainers there that morning! She furrowed her brow and reached deeper. Between the shoes lay a small, silvery stone. As soon as Olive touched it, she felt a gentle tingling in her fingers. The stone was cold and perfectly smooth, as if someone had polished it for centuries. And then something even stranger happened. Tiny flashes appeared where she touched the stone, as if the light was bouncing off the surface in all sorts of shades. The stone seemed to tremble slightly, and there was a cool, fresh breeze from the cupboard that smelled of the forest, even though it was a good half-hour's walk from here to the park. Olive closed her eyes for a moment. When she opened them, she noticed through a narrow crack at the bottom of the cupboard that the floor was no longer what it had always been. Instead of linoleum, she saw patches of soft, green moss. She heard a quiet rustling, as if something small was moving right next to her and whispering a name she didn't know. Her heart began to beat harder. She gently opened the cupboard door. At the same instant, the glow of the stone spread throughout the interior, and Olive felt something unusual lurking just behind the thin wall of the cupboard under the stairs....