The school year was ruled by a chilly September, and everyday life on Silver Street took on a shade of grey. However, the three friends - Lena, Bartek and Maks - knew that their tenement hid more than it might seem. Locals said that an inventor used to live here, who left piles of strange objects behind. Lena loved detective puzzles and had a black notebook in which she wrote down all the strange occurrences. Bartek was a great listener and his dog, biscuit Amber, had a nose for trouble. Maks had ideas faster than the wind, but sometimes too crazy even for his friends. One evening, when Lena was trying to do her homework, she noticed an unusual silence coming from under the door of her neighbour Mrs Rose. The tenement was never quiet - the children shouted, the radio played and Amber barked almost incessantly. Meanwhile, the silence had become so thick you could almost cut it with a knife. When Lena went out into the stairwell, she met Bartek holding Amber on a leash and Maks, who had a torch and magnifying glass in his hand. "Do you hear that too? I mean... don't you hear it?" - whispered Bartek. They all nodded their heads uncertainly. Suddenly, just behind them, there was a quiet creak. Someone opened the door on the second floor. It was Mr Marian, an old man who never went anywhere without his radio. This time he wasn't carrying it by his ear. He looked surprised and even a little frightened. "Where has the music gone?" - he muttered under his breath. Friends gathered on the stairs, trying to make sense of what was happening. Every sound - from the clatter of shoes to the barking of the dog - slowly faded away. Amber looked uncertainly at Lena and curled her tail. The tenement seemed completely different from usual, as if someone had enclosed it in a glass sphere into which no voices, noises or whispered gossip could penetrate. Maks pulled an old map of the building out of his pocket, which they had found in the attic a few weeks ago. On it, he marked the rooms where strange events had occurred recently. "Maybe it's all connected?" - he muttered. Lena jotted something down in her black notebook. Just then, a single metallic clatter sounded from deep in the basement. It was the only sound that pierced the eerie silence. The friends exchanged glances. They already knew they had to go downstairs to find out what, or who, was causing the sounds in their house to suddenly disappear. With torch in hand and Amber leading the parade, they began to walk down towards the dark basement, where the first clue awaited them....