Lena has always been curious about the world, but she never thought that one Thursday after school she would find herself where the boundaries of reality no longer mattered. It all started with the disappearance of the key to the art studio - the one with the heavy copper keyring that looked like an owl. Adrian insisted that something wasn't right here. After all, he had seen the teacher put the key on the windowsill. When they stayed after lessons to prepare posters for the school fete, they decided to look for the key on their own. The school in the late afternoon was completely different from the morning. Empty corridors echoed the sound of their footsteps, and a milky light came through the tarnished glass. Lena and Adrian often joked that the old school hid many surprises. But what they found in the basement, none of them expected. While scouring the nooks and crannies under the stairs, Lena came across a heavy door she didn't know existed. It was bolted shut, but strangely ajar - as if someone was waiting just for them. Behind the door was a narrow, winding corridor with walls covered in peeling green paint. The air here was cool and smelled of dust. The corridor ended with a tall mirror in a baroque frame that looked like it had been taken out of another era. Instead of a reflection of Lena and Adrian, the surface of the mirror rippled slightly, as if it was made of water. Lena walked closer. In the mirror she saw herself, but she was dressed in a completely different way - she was wearing a long coat and holding a glowing ball in her hand. Adrian, usually sceptical, this time could not believe his eyes. He touched the surface of the mirror and suddenly felt his fingers penetrate the glass, as if he were entering a completely different world. Lena looked at him with wide-open eyes. - Adrian, don't do that! - she whispered, but her voice had more curiosity than fear in it. The boy smiled nervously and pulled Lena by the hand. In an instant they both felt their bodies pass through an icy, vibrating tunnel. When they opened their eyes, they were standing in the middle of a huge, silent city made of mirrored towers, and colossal, glittering fish floated in the sky. There was an eerie silence all around. In the distance they spotted a figure that seemed to be waving at them. Lena squeezed Adrian's hand tighter. Was this really happening? Would they find their way back? At that moment, the mirror behind them began to slowly disappear, and shadows appeared around them that looked as if they had just detached themselves from the walls....