The night at the sailing camp today was clear from the milky way. Olek, a fourteen-year-old from Gdynia, was building a radio scanner from a broken ham radio. Yesterday he caught a signal that repeated three notes and one long crackle. Today, he decided to find out where the sounds were coming from, and who they were really about. Nina, his older cousin, was holding a torch and looking into the dark water. Next to her rocked their little yellow boat with its quiet electric motor. Reeds rustled in the distance and a red warning light flashed above the dam. Petty Officer Basia had forbidden going up to Wheel Island after dark, but it was difficult. The signal was simple, but it hid a pattern that Nina recognised after a moment. Three notes marked the letters, and a crackle completed the set, like a dot. Together they arranged the coordinates of a small island in the middle of the Copper Lakes exactly. Basia told the legend of the copper rings that control the water current. After a great storm, the bottom moved and the lake returned something old. Olek squinted and scrutinised the map on his phone without range. The dot pulsed exactly where the petty officer had told him to stay away. - 'Maybe it's just the station echoing,' muttered Nina, adjusting her hood. They pushed the boat away and set off, following the beeps that sounded like breathing. The darkness was smooth and the water carried the boat, like a runway. Above their heads the rope of a bridge swayed, as old as tales of miners. On the island they saw rusted rails disappearing into a dark, low tunnel. The compass was going crazy, jumping like a frog, and the needle was going round and round once. - 'This is not normal,' said Olek, turning the scanner down to a whisper. Then a dry clatter came from the darkness, like metal against metal. Bubbles drifted away from the shore, as if the lake had just taken in air deep. They entered the tunnel, leaving the boat at the edge where the rope rustled against the concrete. The walls had copper tiles, cracked, with the year and lightning sign scrawled on them. - 'Eighty-seventh,' read Nina, touching the letters that were as cold as ice. The scanner beeped suddenly, and a voice from the noises whispered their names, indistinctly. Olek glanced at Nina, but an alien beam of light came on in the tunnel. Someone must have entered from the other side, because the echoes carried footsteps closer and closer. The wheel on the steel door moved on its own, creaking as if it had waited a long time. The water in the passage trembled, and something underneath began to emerge slowly.