Somewhere on the outskirts of the city, in an abandoned observatory, Lena, Michal and Kuba used to meet. This was their secret base - a place where they made plans, built inventions and dreamt of faraway journeys. One summer afternoon, as a storm hung overhead, Lena unexpectedly caught a bizarre signal in the old radio telescope. A sequence of repetitive beeps came through the noise: pip-pip-piiiip, pip-pip-piiiip. Michael, the technical genius of the group, quickly began to process the signal on the computer. "It's some kind of cipher!" - he exclaimed excitedly. Meanwhile, Kuba was trying to glue the pieces of sound together. After an hour, he came across something neither of them expected - a diagram of a triangle with three dots emerged in the noise. Lena recognised the symbol immediately - she had seen an identical one in old photos of the Mars rover. - Do you think it's someone from Mars trying to contact us? - she asked in a whisper. - Or from Proxima Centauri! - added Michael, who always had his head in the stars. Without waiting long, the children decided to build a receiver to better capture the signal. They worked through the night, amid candles and the rustling of leaves outside the window. Finally, as the first rays of dawn came through the dirty windows of the observatory, they heard a a voice. Quiet, intermittent, as if someone was speaking from very far away: - ...help... this is Proxima 3... we need... find the key... The friends looked at each other in disbelief. They were the first people to receive a message from another planet! But what was the "key"? And where to look for it? At that moment, the radio telescope began to vibrate strangely, and an unknown virus appeared on the computer screen, which independently saved a file with a puzzling sequence of digits on the desktop. Michael was already stretching his hands to the keyboard when suddenly the light flicked on and more mysterious words came from the old speaker. Before they had time to react, the observatory door creaked open slowly....