Lena carefully moved her finger across the control panel and glanced at her friends Nikolai and Sarah. They were sitting inside a small spaceship which, although built in Lena's backyard garage, looked very professional. The girl had bright hair tied in two braids and eyes that always lit up when she heard the word 'space'. - Ready? - Lena asked, lowering her voice, as if she feared that someone from outside might overhear them. Nikolai, who was sitting in the left-hand pilot's seat, nodded. He was the oldest of the three and wore large glasses through which he looked at the screens and monitors with the seriousness of a real engineer. - 'Engines on, systems ready, we've got the green light! - he reported, pretending to be the voice of a computerised robot. Sara bared her teeth in a wide grin. - 'I'm waiting for take-off! - she exclaimed, peering through the porthole at the night sky full of stars. Lena breathed deeply, then pressed the big red button. The ship vibrated and blurry lights appeared outside the windows - they had set off on their journey beyond Earth, leaving all that was familiar behind. Their destination was the asteroid belt beyond the orbit of Neptune. There, according to recent radio readings, drifted an abandoned research station that no one knew where it had come from. Feelings in the cabin were growing - a mixture of excitement and slight anxiety. After several hours of flight, when all around was a deep, cosmic silence, Lena first noticed a strange, glowing silhouette blurred among the rocks. - See! - She whispered, and her finger went to the glass. The station looked like a huge metal necklace abandoned by a giant creature. Blue lights flashed around it, and a quiet, pulsing signal came from within. - 'I think it's a welcome signal... or a warning,' murmured Nikolai, listening to the strange sounds coming from the loudspeaker. Sara was the first to decide to leave the ship. Dressed in a silver jumpsuit, she fastened her helmet and pressed the button that opened the airlock. - Come on! - she encouraged the others. All three of them slowly moved towards the station's huge gates. The door, though covered in dust and micrometeorites, unexpectedly hissed and swung open with a quiet swish, as if inviting them in. Beyond the threshold, twilight reigned. Dust particles floated everywhere and strange symbols they had never seen before shimmered on the walls. Lena took out her torch and illuminated the corridor - it stretched far, and a soft green glow flashed at the end of it. Nikolai approached the control panel at the entrance. He tried to start the computer, but instead of the normal response, a deafening chime sounded and bright red lights came on. At the same moment, a metallic rustling sound came to them from deep within the station.... The children looked after each other with a mixture of fear and fascination. What was waiting around the corner? Who are the creators of this station and what was its purpose? Lena took the first step towards the corridor, not yet knowing what they were about to discover....