Tosia loved watching the starry sky from the window of her room on the thirtieth floor of a high-rise building in AeroCity. The city never slept - silent magnetic vehicles drove on the streets and courier drones twinkled in the sky at night. However, Tosi's greatest curiosity was about the stars. Every night she wondered if someone, somewhere far away, was looking at her planet the way she looked at distant worlds. One day, as lessons at the School of the Future were coming to an end, Tosia noticed her best friend Igor staring at his mini-computer screen with a strange expression on his face. - 'Tosia, check this out! - he called out, running up to her. - A strange signal has appeared on my receiving antenna! It doesn't look like any we've received so far. It's as if someone... is trying to tell us something. Tosia looked at the boy in disbelief, but quickly remembered how many times Igor had found unusual transmissions during his electronic experiments. This time, however, the matter seemed more serious. The signal repeated every few minutes and sounded like a series of strange pulses: short and long, as if someone was trying to tell them something in an unknown code. After lessons, the children met in the secret inventors' club, which was housed in an abandoned hangar behind the park. There were planets hanging on the walls and Igor's self-built telescope stood in the corner. They set up the equipment and played the signal again. This time Tosia could also hear it: „pip-pip---pip---pip---pip-pip”. - 'It's definitely not an ordinary weather transmission,' Tosia said. - Maybe someone is really calling us... from outer space? Together they wondered how to decipher the signal. Igor plugged the computer into the scanner, trying to fish out more information. Suddenly, strange symbols they had never seen before appeared on the screen. They looked a bit like geometric figures, a bit like letters, and a bit like the pawprints of an unknown animal. - Do you think this could be a map? - whispered Tosia, completely absorbed in the events. Before they had time to think about it further, the hangar was lit up by a bright flash of lightning. Their equipment began to beep, and the telescope rotated on its own, pointing to the farthest part of the sky. At the same moment, another pulse sounded from the loudspeaker. This time it was longer and clearer. Something outside began to move.... The children looked at each other in surprise. They felt that they had just crossed the boundary of ordinary adventures. Tosia squeezed Igor's hand. They had decided: they had to find out what - or who - was sending them this signal. Only... are they ready for what might await them outside the walls of the AeroCity?