Zorion, Lea and Miko sat on the edge of a huge crater that shone with a soft, silvery light. Ever since their families arrived on Silverion - a planet orbiting a cold star - every day brought something new and sometimes frightening. Zorion, the eldest, was already fifteen years old and always looking for an opportunity to discover something unusual, even if it involved risk. On the other side of the colony, among the rocks resembling frozen waves, strange phenomena were taking place. Last night, the communication system picked up a signal with an unusual frequency. The signal was rhythmic, like a heartbeat. None of the adults could decipher it. Although the children were officially forbidden to leave the designated zones, Lea, a talented programmer, surreptitiously copied the data onto her holowatch. In the afternoon, while the rest of the colonists slept after the night shift, all three slipped outside the secure area. The sand under their boots was slippery from an unknown mineral that glowed in the darkness. They approached the cave from which, according to Leiny's calculations, the signal had come. - Do you think this is definitely a good idea? - Miko, the youngest of them, asked in a whisper, looking around nervously. - 'If it's just a simple malfunction, we'll go back. But if it's something more... we need to see it,' replied Zorion, trying to hide his own anxiety. They went inside. The air smelled of metal and the walls were covered with strange luminescent patterns that they had not yet seen in any official report. For a while, no one could be heard - even their breaths seemed muffled by an unearthly echo. Then Lei's holowatch came to life. A new sequence of symbols appeared on the screen. Suddenly, the light inside dimmed, and a deafening, inhuman sound came from the depths of the cave. Zorion took a step forward, and then the ground beneath his feet began to pull apart, revealing a spiral staircase leading downwards - where the signal pulsed ever stronger....