The Saturn 7 station drifted peacefully in the orbit of Mars, enveloped in the darkness and cold of space. Life here followed a steady rhythm: wake-up, lessons, exercises, chores. For most of the inhabitants, this was the usual routine, but for fifteen-year-old Leo, everything seemed different lately. Ever since he heard that strange, pulsating sound in his headphones while studying at night, he couldn't stop thinking about it. Leo hadn't mentioned the signal to anyone – not even his twin sister, Mai. However, that night, he couldn't stand it and let her in on his discovery. In their shared room, with the windows covered and the communicators muted, he told her every detail. 'It wasn't just a noise,' he said poignantly. 'It sounded like… Like the echo of a familiar voice. Or like a code. I tried to record it, but something was interfering with the signal.' Mai wasn't so inclined to believe in cosmic mysteries, but seeing Leo's determination, she agreed to help him. That night they sneaked off to the engineering section, where the station's main computer was located. With the help of some hacked software, they traced the source of the sound. To their amazement, the signal was coming from external antennas and its frequency was not listed in any available registers. 'That's impossible,' whispered Mai. 'After all, such frequencies are blocked. Someone must have done it on purpose.' Suddenly, the door to the technical section emitted a quiet click. An unrecognised symbol appeared on the main computer screen: a geometric spiral they had never seen before. At the same moment, the station shuddered slightly, and the pulsating sound in Leo's headset resounded again, this time faster and clearer… As if something – or someone – was answering directly to them.