The evening light was streaming in through the window of the biology room, painting geometric patterns on the floor. Leon was finishing jotting down his homework when something on the windowsill caught his eye - a shiny dark blue pebble, as if completely out of this world. Next to him, Maja, always curious and adventurous, glanced over her shoulder. "Oi, where did you get that?" - she whispered. Leon shrugged his shoulders, because he didn't actually know himself. The pebble had appeared in his pocket after today's strange dream, in which he was running around an empty city and the shadows seemed to be talking to him. As soon as he touched the pebble, he felt a chill. The loud laughter of his colleagues from the doorway suddenly quieted. It became strangely quiet. Leon looked towards Majka. "Oi, Leon, where are you?" - she asked with concern, looking around. He looked at his hands - he couldn't see them. In a panic, he stood up, and the chair made a creaking sound. Maja looked straight at him, but her gaze flicked across him as if he wasn't standing there at all. An alarm siren sounded in the corridor. For a moment Leon wondered if it was all a dream. But then he heard someone's muffled shout through the open door: "Someone has disappeared again! Again!" Maja came closer and grasped the air where his elbow had just been. Leon felt her touch, but she felt nothing. "If you can't see me... can I find out what's really going on here?" - he thought. A blue light flashed outside the window and a strange black silhouette flitted across the schoolyard. Leon knew he had no time to waste. He silently dashed through the door into the corridor, sensing that his new powers were only the beginning of a much bigger mystery. The smell of ozone was in the air and the echo of his footsteps echoed off the walls of the now empty wing of the school. The door to the old computer room was ajar, and a faint orange glow shimmered inside....