February in Piwnice was sharp as glass, but the sky today had the clarity that astronomers dream of. The thirty-two-metre dish of the radio telescope stood on a metal structure like a huge white ear, listening to the universe. From the control window it could be seen turning very slowly towards the north. Inside, it smelled of dust, coffee and ozone from the old equipment, which crunched quietly as if speaking among themselves in an old dialect. Lena stretched her hands over the radiator and watched the scrolls of coloured lines on the monitor. On one screen, a spectrogram was moving - bars of energy at different frequencies; on the other ran the digits of time and coordinates. She pressed her eyebrows together until a wrinkle appeared on her nose resembling a pause in the notes. - See,' she muttered, tapping the screen with her fingernail. - Here. At around one thousand four hundred and twenty megahertz. There should be just a hum, and we've got spades. Igor pulled up a chair, which beeped in such a way that Lena flinched with her whole body. He had big headphones that usually hung around his neck, and perpetually tousled hair, as if his head was a private storm field. He sat down with seriousness, as if he was about to solve a crossword puzzle at cosmic speed. - 'Hydrogen line,' he said. - A natural signal. But this... - he squinted. - It looks like modulation. - So someone out there is nodding at us? - joked Lena, pretending to be carefree. But when she clicked the zoom button, a clear sequence of short 'fleeces' and longer 'flubs' of energy appeared on the screen. - Okay, this is no longer funny. A clock hung on the wall, which seemed louder at night than during the day. The ticking filled the gaps between the clicks of the relays. In the corner of the room a small robot hoover slid along the cable, too faithful to sleep, too old to collect anything but its own shame from the linoleum. - Dr Fijałkowska? - called out Igor, leaning into the intercom microphone. - I think we've got something. There was a whine on the loudspeaker. - I'm on my way - replied the mentor's voice. - Just don't touch the filters. And don't move the plate without permission. You have five minutes to record samples. Lena opened a new data buffer. The graphs went noisy, but against a background of grey creeping like fog in the mountains, clear lines shone. Short-long, short-long, pause. And again. - Maybe it's a reflection? - she muttered, without looking at Igor. - A plane, a satellite, a balloon? - She choked out the list she'd been churning out since the first day of the 'Astrolab Junior' camp. - 'A balloon wouldn't hold the frequency like that,' replied Igor. - A plane would give a different displacement. And a satellite... - He looked at the clock. - Well, that's right. Orbital overflights we have reviewed today. Empty at this time. Doctor Fijałkowska came in, pushing back a strand of grey hair from under her cap. She always looked as if she was a little faster than the rest of the world, as if catching up with her own thoughts on the run. She watched the screen, silently, then leaned over the console and immediately straightened up. - 'It's linear and consistent,' she said slowly. - But the source... - She moved her finger over the elevation graph. - See. We have an azimuth heading north, elevation low. As if above the horizon, but... I didn't inform anyone about the tests. - You mean someone is waving a torch over our heads from orbit? - Lena asked, with a nervous laugh. - 'From orbit I'm the one who gets advance notifications,' reflected the doctor. - Besides, the modulation is... strangely repetitive. - She looked at them sharply. - Don't invest in theories. Collect data. Lena couldn't look away. She tilted her head. Something stupid suddenly occurred to her, so of course she did it: she tapped her fingernail twice on the table top - once briefly, once long. On the screen, after a second's delay, something that looked like a reflection of that rhythm appeared next to another series of signals. A short, a long, a pause. - Did you see? - she whispered. Igor froze. - No kidding. - 'Do it again,' Doctor Fijalkowska instructed, in a tone that was both a command and a request. - And record a separate time stamp. Lena tapped again, this time very clearly: short, short, long, short, long pause. The signal on the screen sort of applauded on the other side: short, short, long, short - pause of the same length. It was not a perfect shadow, more like a response through a thick glass. - 'It's not natural,' whispered Igor. The doctor closed his eyes. - 'Okay. We're not panicking. - Then, as if recalling a paragraph, she added: - 'The system is not designed to broadcast. We can only listen. But we need to check for a local source outside. A stimulus. Anything. Igor, Lena - you come with me to the service door. Just to the railing. We don't enter the structure without technical approval. Their jackets crunched as they put them on in a hurry. The cold pasted into their cheeks like a thin film. Outside, everything seemed bigger than it was inside: the massive footing of the structure, the steel trusses drying in the moonlight, the red warning lights blinking rhythmically. From the upper platform there was a platform leading off to the focal cabin - a small box suspended like fruit in an antenna garden. - Just to the railing,' Doctor Fijałkowska repeated. - We look, we listen, we come back. Lena pressed her hands against the metal railing and immediately withdrew them. Frost capped her like a dog, but that wasn't what stopped her. On the steel pipe, where the steam from their breaths settled and froze, tiny lines appeared: short and long, arranged in rows. A winter ornament? No. It was too even. - 'Igor,' she whispered, touching her finger until the marks froze to her skin. - Can you see it? He leaned over the railing. Intervals were traced on the thin layer of frost, in a single row. A short one, a long one, a pause. Then again. - A breeze? Vibration? - enumerated the doctor, but her voice was hushed as if in church. - God... - she added almost silently, not out of prayer, rather out of helpless calculation. Somewhere below, the wind rustled, carrying with it the smell of wet branches and something like the heated dust of machinery. Metal purred as the elevation mechanism moved the plate a fraction of a degree. Lena lifted her gaze and saw that the entire large disk was lazily submitting to commands from within, yet the control board showed a manual mode. Nobody had pressed the switch after all. - 'Don't touch anything,' the doctor said, already over the intercom, as she had sent them a step earlier, and stopped by the door herself. - And don't get on the platform. Lena's phone vibrated in her pocket. She pulled it out and looked at the list of networks. Besides the familiar "CA-UMK_Gosc", another name appeared, in a strange alphabet and without dots: "SLYCHAC_TO". She smiled nervously. - 'It's a tech joke,' she muttered, not really believing her own words. - 'They don't have such a sense of humour,' Igor commented. - Do you remember their kettle? It's a museum. - 'We're going back,' decided the doctor, in a tone that brooked no opposition. - 'We'll report it and keep watch until the night engineer comes. At that moment the internal speakers, those mounted outside under the platform, coughed and beeped briefly, as if someone were trying to connect the wires with their tongue. Then three clicks sounded - the same length and pace that they had seen on the screen. They stood still, as if the sound could see them. - Who's there? - fired out Lena before she could bite her tongue. A metallic clatter came from the focal cabin, faint but distinct. Like someone running their hand over aluminium foil. Then - the answer: short, short, long, short. - 'We're not going in,' the doctor reminded her, although it sounded as if she also had to say it to herself. Igor took half a step towards the platform. He used to tell Lena that he was afraid of heights. Now he didn't look frightened - more like mesmerised. He pulled a small sensor from his pocket, which he had assembled overnight from parts ordered in secret from his parents. The device flashed an LED and began plotting graphs on his phone. The pulse at the cabin was higher. As if something was breathing in there. Or it was counting. - 'Lena,' he said quietly. - It's close. A low-priority alarm beeped on the console inside the warm control cabin. At the same moment, the handle at the door to the platform - the thick, secure one - rattled, as if a bolt had been released. The red warning lights stopped blinking and went on solid. The door swung open a centimetre, then two, leaving a gap from which blew a dry chill and something else: a faint smell like ozone after a storm. - Stay! - shouted Dr Fijalkowska, but her voice crumbled into metal. - Don't take a step! Lena didn't. At least not with her feet. Instead, the hands - the palms had a plan of their own. One, as if acting independently, stretched towards the door handle. She felt that it was idiotic, dangerous, that when she told her mother about it, the latter would swear not to let her go to any camp again. And yet the proximity of something that corresponded to them on the other side of reality was like a magnet. A light flashed through the gap. Not bright, not white. Rather, a gentle, milky blue, pulsing in a rhythm they had learned in the last hour like the alphabet. Short, short, long, short. Pause. Again. Lena's phone flicked once more. On the screen, with no notification and no app, the words that could not appear appeared: "I HEAR". Followed by: "WAIT." The letters seemed to arrange themselves from the noise of the pixels, then blurred, like footprints in the frost. - Don't touch," hissed Igor. His pupils were dilated and his hands were clenched into gloved fists. Lena held her breath. Everything slowed down: the wind, the ticking of the clock, the cold air. The handle of the focal cabin moved on its own, by a hair, as if someone had a hand on the other side too. And from inside came three quick knocks, exactly like the ones on the screen minutes before. The handle vibrated a second time.