Lena stood on the roof of the school with a sieve antenna. Olek held a small radio that buzzed like a wasp. The wind hummed all around, and the playground glowed with empty lamps. The roof smelled of tar, and far away a train rumbled. It was supposed to be a simple rehearsal of club communications. Lena turned on the recorder, just as the circle keeper had taught. Instead, something answered, as if it had been waiting for a long time. First they heard an even pulse, as if someone was punching out a code. The signal had a constant interval, exactly every two seconds. The app on Lena's phone turned the pulse into letters. Her name and a down arrow flashed on the screen. Then numbers popped up and the words: "BASEMENT, ENTRANCE B". Olek swallowed his saliva and looked at Lena. "Maybe it's a Sixth F joke?" he whispered. They walked down the stairs by the hall to the heavy door of B. A rusty sign warned of a sports magazine. The radio quieted as they moved away, and intensified at the door handle. Lena touched the metal and the antenna trembled. The same rhythm came from inside, but deeper and closer. The lock clicked as if responding to their arrival. The door swung open and a strip of blue light slid out. Shadows glided across the floor, as if swimming underwater. In the centre stood a smooth sphere, larger than a ball. Its surface reflected faces but added a second smile to them. The radio crackled and said in Lena's voice: "Don't touch." Olek was already extending his hand when the ball opened a gap. Something inside it blinked like the eye of a camera and called them by name.