Maks knew that their holiday at his grandmother's would not be the same as always. As soon as his mum left on the first day, there was a heavy smell of dust in the air and the old boards creaked with every step. The house where grandma lived was huge and full of nooks and crannies. Kalina, Max's younger sister, used to laugh that the cat's ghost lived there, because every now and then they would hear knocking in the attic. One cloudy afternoon, while Grandma was napping in her armchair, Maks and Kalina looked in the drawer in the living room, where old photographs always lay. This time there was a rusty little key lying next to the photographs. Intrigued, they began to search the house for a lock that matched the key. They searched in the attic and basement, but found nothing. It was only in the evening, when they were returning to their rooms, that Kalina stopped on the stairs. - Did you hear that? - she whispered, grabbing Maks' hand. There was a low, teasing whisper coming from behind the glass door under the stairs. No one ever went in there; the door was always locked. Maks remembered his grandmother's warnings: "No one looks under the stairs. It's a place for things that are better left alone." - Maybe... maybe it's the wind? - he suggested uncertainly. But then they heard clearly: someone calling their name, once, twice, louder and louder. Kalina tightened her fingers on the key they had been holding since the afternoon. - 'Come on, let's try,' she whispered, putting the key to the lock with trembling hands. The door creaked, the air grew strangely cold. There was darkness inside, as if all the light had been absorbed. For a moment Maks thought he saw a shadow moving across the wall, and an old notebook with a stained cover lay on the floor. As Maks reached out to pick it up, a slamming sound came from behind the wall and the door slammed shut behind them on its own....