After lessons, Lena climbed onto the roof of the old school. The observatory had been closed for months due to renovations. No one had looked up there, and she had a key from the watchman. In her backpack she carried a soldering iron, batteries and a damaged receiver. She wanted to use it to make a small radio telescope for experiments. Instead, she heard a strange tapping from a closed cupboard. Inside lay a metal cube with the inscription: Hyperphone Module. Underneath, someone had roughly written in marker: Do not switch on. Lena carefully plugged the cube into her large powerbank. The device immediately vibrated and lit up with a dull blue light. An illuminated map of their town appeared in the air. Dots glimmered, and one pulsed exactly where she stood. Lena tapped the housing, and the dot blinked in response. Numbers popped up under the map: depth minus three metres. A second dot lit up under the floor and began to grow. A low buzz came from the box, consistent with her pulse. The floor vibrated and the screws in the corners moved slightly. A cold gush came from the ventilation grille, like a refrigerator. The speaker in the ceiling hummed and whispered her name: Lena. She tried to switch off the cube, but the switch was stuck without moving. On the map, the second dot climbed towards the surface faster and faster. An even scraping sound came from under the tiles, as if someone was counting steps. On a small flap she was unaware of, a lock had slid away. A thin line lit along the gap, then a glow spread. Lena leaned over and whispered: Hello, is anyone there? From below it clattered five times, the exact rhythm of her name. Then something flashed in the darkness and began to slide out.