On a rainy afternoon, four people hid from the downpour under the porch of School Complex No. 4. Olive pulled a wet copy of a Stephen King novel out of her rucksack, Zuzia glanced at her phone screen and quietly commented on the news, Dawid whispered something to Bartek, who laughed under his breath. However, they all froze when an unfamiliar voice came from the depths of the corridor: "If you're looking for something to do, the Old Library is open." They looked at each other in disbelief. The Old Library building - officially closed to the public for several years - had always captured the imagination of local teenagers. Rumours of forgotten cellars, labyrinthine corridors and amazing collections meant that a brave few tried to look in there after dark. Today, however, no one was planning any expedition. And yet... Olive, cooking from her books, looked at the others: "Well what? After all, we can't waste an opportunity like this." David smiled broadly and Bartek nodded: "If you're scared, you can stay." - he threw to Zuzi. The latter only replied: "Come on. Let's go." The historic edifice creaked quietly under the pressure of the door. Inside, there was the smell of dust and wet shelving. Deep inside, Bartek's torchlight illuminated a particular section of wall covered in thick cobwebs. On the marble floor lay a thick, dusty book with a brown, cracked cover. They looked at it - it bore a mark resembling infinity, crossed by a vertical line. Someone must have left it here recently, because there were no traces of the old dust on the tabletop. Curious, they began to search their surroundings. Olive, guided by intuition, pressed the cover of the book at one point. The wall began to move slightly, as if under the pressure of a hidden mechanism. Instead of another bookshelf, a narrow corridor appeared behind the wall, bathed in a bluish light that was nowhere else in the library. "Did you see that?" - David stared wide-eyed at the girl. Susie shone her torch into the depths of the corridor. Bartek, the first, took a step forward, driven by curiosity and courage, and slipped inside. They walked carefully, trying not to make any noise. With each step, the light became more intense and the walls of the corridor seemed to change texture - they became smooth and cold, shimmering with a metallic glow that was impossible to describe. Finally, they came to a door that looked completely different from any they had seen before: tall, glazed, with a pulsating blue light around the frame. They looked as if they were hovering a few centimetres above the ground. In the middle was a plaque with the same sign as on the cover of the book. "Maybe it's better not to..." - Zuzia started, but Bartek had already put his hand on the plate, and the door slowly began to open. Behind them stretched a space that was unlike anything they knew from their world. The air was thick and electrifying, and the view beyond the door completely incongruous with the old library. The hulk of a huge city with endless bridges hung in the air, and somewhere far away the silhouette of a being with long, shimmering wings flashed by. Everyone froze for a moment, hearing a strange sound behind them, as if someone was closing a passage. They jerked around, looking at each other in disbelief, asking themselves the same question in their minds: should they go further in, or is it too late to go back?