The Stefan Banach School was like most schools - grey, well-kept, with endless corridors and halls with large windows. But something happened this autumn that made even the most jaded pupils look at things differently. Lena was sitting on the windowsill, watching through the foggy glass the leaves swirling on the school playground. At her side stood Wojtek, munching corn crisps from his sweatshirt pocket. Their conversation was interrupted by the sound of the bell, but at the same moment something else caught Lena's attention. - Have you noticed that the bell has been sounding quieter and quieter since Monday? - she asked. Wojtek shrugged his shoulders. - Maybe the neighbouring class is testing new headphones? They both laughed, but just a moment later the whole school witnessed something unprecedented: on Wednesday morning the bell simply... disappeared. Everyone standing in the corridor looked at each other in disbelief. Teachers ran around confused, trying to work out when their next lessons should start. Pupils - either delighted or stressed - exchanged theories ranging from 'hacker attack' to 'school gaining time freedom'. Lena couldn't stop thinking about it. She decided that she and Wojtek would discover what had happened to the bell. After lessons, they sneaked towards the headmistress's office. There, they noticed something they hadn't expected - tiny flashes of light coming from under the door of an old technical laboratory that no one had used for months. Wojtek looked at Lena questioningly. - 'Do you see the same thing as me? Lena nodded. Both their hearts beat faster. They walked slowly closer. The door was only slightly ajar. Through the crack came a sparkling sound, reminiscent of a quiet bell. - Are we going in? - whispered Wojtek. Before she had time to answer, something moved inside and the light suddenly went out.