It was perpetual morning at the Heath base, although there was no sky beyond the lock. David Gorski supervised algae farms and antennae, drinking water that tasted of metal. Heath lay at the edge of the Sea of Tranquillity, in a place without odours or winds. A picture of Earth hung on the wall, suspended like a lantern above a steel desk. David liked the silence of the server room, the even hum of the pumps and the static crunch of dust. He said it was the only music the moon would not silence. When the console blinked red, he thought it was another false alarm. However, the signal was clear and close, transmitted just a few hundred metres below the regolith. The owl, a support system, displayed a graph: the repetitive pulses arranged themselves in a familiar rhythm. After a moment, he realised it was his name, given in the code of the old probes. - Owl, the source? - he asked. - Location: Rybka crater, sector four. No entry in the base documentation,' she replied. A Lis-3 rolled through the airlock, a small vehicle with seven micrometeorite dents. David checked his suit for leaks, clipped a guide line into his harness and set off for the plateau. The ground hung over the horizon like a pupil, and the shadows of the equipment lengthened like knives. The signal grew, the pulses quickened, intertwined with their own breathing and heartbeat. - Can you hear it, Owl? - I hear it. Correcting the path three degrees east,' came the reply. The Rybka crater turned out to be a fissure, at the bottom of which something glowed beneath the dust. David slid down the anchor and shrugged off the panel, bringing out a mission logo he didn't know. The steel flap bore the inscription: PION-2, date 2041, evacuation instructions in Polish. - 'There was no PION-2 on the moon,' he said into the microphone, though no one denied it. The panel flashed as he touched it with his glove, and asked for an access code. He typed in the standard, rejected. Then the letters formed themselves: Hello, David. Privileges granted. The mechanisms creaked, small pebbles shook, and a narrow gap let out a plume of dust. The interior was dark, and a single green LED glowed in the depths. A short sigh, so similar to his, flowed from the speaker in his helmet that his throat was squeezed. - 'Dadiu,' whispered the voice, using a nickname no one had pronounced in years. The owl raised the radiation alarm, and a warning triangle flashed on the inside of the viewfinder. Something knocked on the inside three times, slowly, as if teaching him a rhythm.