The old building on Sunny Street had been abandoned for years. Most of the townspeople avoided it by a wide margin, but for Ola, Filip and Zuzy it had always been a source of fascination. One June afternoon, they decided to take a look inside - not for the first time, but this time something was different. The door, which was usually bolted, stood ajar. Philip, as usual the bravest, pushed it open slightly. The interior smelled of dust and damp, and their footsteps echoed down the long corridor. The light coming through the broken windows created fantastic patterns on the walls, resembling maps of unknown countries. - What if we meet someone there? - whispered Zuza, a little withdrawn. Ola laughed quietly. - The only inhabitant of this tenement is an old armchair, if it hasn't already been eaten by moths. The friends entered the living room, where refined parties must once have taken place. Now the same dilapidated armchair stood in the middle, and next to it - a huge, cracked mirror they had not seen before. Philip walked closer. There was no reflection at all in the sheet. Instead, he saw something there that was hard to describe - grey clouds moving over an unfamiliar city made of crooked towers and glowing, floating bridges. The longer he looked, the clearer the image became. After a while, Ola and Zuza also looked in the mirror. Each of them saw something a little different, but they were all certain - this was no ordinary illusion. Suddenly, as if the mirror sensed their presence, it made a quiet sound, like a whisper of wind. A swirling streak of light appeared on the surface and began to grow, creating a passage of sorts. The room trembled and the air became heavier. - 'I don't think this is a good idea,' muttered Zuza, taking a step back. But Philip was already reaching out his hand to touch the swirling light. At the same moment, something jerked them all forward - they felt the ground beneath their feet disappear and colours and shapes appear around them that were unlike anything familiar from everyday life. And then...