The old town library seemed to Kacper a place completely devoid of magic; the shelves bowed under the weight of dusty tomes, and the light coming through the stained-glass window created a mosaic of colourful spots on the floor. Nevertheless, this was where Kacper and Lila spent most of their free time, poring over books and talking about anything that didn't fit in with the grey world outside the windows. That day, while looking for an old atlas, Kacper discovered a door in a side corridor that he had never seen before. The rusty handle resisted, but eventually gave way. Behind the door was a small room. On one wall hung a huge mirror in a heavy silver-plated frame. Its surface was astonishingly clear, almost like a sheet of water. - Look, this is probably the oldest exhibit in this library! - whispered Lila, touching the frame. At the same moment, the light in the room dimmed and the reflection in the mirror shimmered with a strange blue glow. Kacper stepped back, but Lila, as if mesmerised, took a step forward. - Can you see it? - Kacper asked, looking at her reflection, which had begun to blur and lose focus. Instead of the usual interior of the library, a maze of winding paths and glittering balls of light appeared in the mirror, floating in the air like skylights. - 'I think it's a ... a portal,' Lila whispered. Kacper felt his heart speed up. He moved closer to the mirror and noticed that his own reflection was no longer following him - instead, he saw a figure that appeared to be wearing his clothes, but whose eyes shone with a blue light. Before they could say anything more, the mirror lit up with a blinding light. A low, throbbing sound rang in their ears. Lila held out her hand, as if drawn by an invisible force. Something - or someone - on the other side of the portal moved violently, and the air in the room swirled. Lila looked at Kacper: - Are you coming in with me? Suddenly the floor beneath their feet trembled, and a quiet whisper came from the depths of the mirror....