Ola and her younger brother Franek were holidaying with their grandmother in the countryside. The big house had lots of nooks and crannies and old furniture to explore. One rainy afternoon, they decided to climb into the creaky attic. There, between boxes full of toys and books, was a huge old wardrobe. - Let's go and see what's inside! - whispered Ola with a glint in her eye. Franek nodded, although he was a little afraid. The wardrobe door was cold to the touch. When they gently opened it, they saw.... darkness. Inside they could hear a quiet rustling, as if someone was moving on the other side. - Maybe it's just a mouse of some kind? - suggested Franek, squeezing his sister's hand tightly. But then a soft light began to emerge from inside the wardrobe. One of the shelves slid out by itself, and a mysterious, shiny key appeared. Next to it lay a piece of paper with the words: "Whoever finds the key will discover the secret of our house...". Suddenly a whisper came from the depths of the wardrobe: - Come in if you dare....