The storm had gone, but the smell of iodine and sweet rust remained in Brzegowice. At the fish market, between crates of cod and damp newspapers, one story was repeated: at four o'clock in the morning, something shone in the old lighthouse on the islet. Someone saw a pale streak of light cutting through the fog. Someone else took a blurry photo, and the comments underneath were full of sneers and swears. Everyone knew that the lighthouse had been out of action for a long time. The electricity has been cut off, the stairs are scarred, and in season tourists only take selfies on the bridge. Lena couldn't get past the rumour. It smelled like promise. She had been learning to listen to the sea since her grandmother had told her that some things whisper to those who want to hear them. It sounded funny, until Lena realised that sometimes she really did feel a tremor inside her, as if there was a thin string in her chest that something could move. - 'It's probably the headlight from the fishing van, reflected in the clouds,' Kaj muttered as they stood at the base of the narrow bridge. He was fifteen years old and his pockets were perpetually full of tools. He installed apps on his phone that no one but him understood, and made equations out of stories about single flashes. The bridge lock lever was covered in salt. The chain had long since been cut by someone, and the planks crunched underfoot like bitten nails. Down below, between the rocks, the remnants of the storm were bubbling, and the mist - devoured and blotted out by the wind - hung over the islet like a damp curtain. The lighthouse rose from the granite like a white bone. Its neck was ringed with seagull nests, its tin door rusted, and shadows of rope and lichen ran along the walls. On the threshold lay a flat, dark stone, smooth as glass. Lena leaned over: the surface of the stone showed the outline of a circle, as if someone had touched it with the same hand so often that it had left a mark. - They said the lantern was dead," she whispered. - And yet something had woken her up. The entrance smelled of old dust, salt and grease. The cast-iron stairs creaked as they climbed higher and higher, and the walls glistened with a thin layer of moisture like leather after a rainstorm. Underfoot rattled broken shells and small pebbles that someone had once brought in and never brought out. Halfway down, next to a niche with a broken window, stood a lamp case. Inside lay a metal ring, toothed like a clock. Lena ran her finger over the marks carved into it. They were not numbers. Rather, short words: silence, electricity, breath. - 'Look,' said Kaj. He pulled a small compass out of his rucksack, like the ones in scout kits. The needle did not point north. It was pirouetting, stopping, moving again, as if something underfoot was changing its decision every now and then. - This is not normal. At the very top, they were greeted by a glass circle of lens, edged with metal like lace, flecked in one quarter with thin web-like veins. Close to the glass, the air was cooler, and when Lena leaned over to look through the gap, she felt a metallic aftertaste in her mouth. It was as if something was pulling the heat from her breath. Under the windowsill lay a notebook, soft from the dampness, bound together with a rubber band. Two letters stared from the cover: A.M.. - 'Don't take it,' Kaj warned, but it was too late. Lena swung back the rubber band and looked through the entries. The writing was slanted, strong. The date: 1989. Descriptions of tides, wind seasons, small drawings of a lens and some diagrams, which Kaj immediately photographed. One sentence vibrated between the notes: If you apply sound, the glass responds. Scale: A 110 Hz, E 164.8 Hz. The old light remembers. - Sound? - Lena repeated. - Like a camertone. Kaj fired up the guitar tuning app on his phone. The screen brightened and the clear, thin sound of the letter A spread through the lantern. It was so even that Lena felt it lower than her ears - in her oesophagus, under her sternum. The lens didn't light up like in the movies, but something had changed. The sea birds outside had stopped screaming. The mist near the glass thickened and began to arrange itself in filigree swirls, like smoke being drawn into the lungs. - Again,' said Lena. - Give it a little quieter. When the sound rang out a second time, the toothed ring by the lens vibrated. Kaj put his hands on it. The metal could not be forcibly turned, but under the tremor it shifted by a tooth. The teeth clattered, a quiet click could be heard. An uneven line flashed from the side, thin as a blade. Not light from the current. Something softer, as if a fragment of the day by someone else's hand had been cut off and hooked in the air. The lantern drew in a deeper breath. You could really hear it: the irregular sucking in and releasing of air, like the work of hidden bellows. Lena felt the hair on the back of her neck stand up. Her mouth was dry, but the inside of her hand felt cold, as if she were holding snow. Through her lens, she saw the sea - as usual, dark blue, fallen under the weight of the sky - and something else. The edge of the horizon line seemed to split. Behind the familiar straight line outlined another, slightly curved one. Between them flashed windows that no town on this side had: long, narrow, made up of tiny panes. And a light that was not the sun. - Can you see it? - Kaj spoke up in a whisper, as if afraid of waking something that was only pretending to sleep. - 'I see it,' Lena replied. Her voice was different from usual: deeper, as if the A sound was still shaking the strings in her throat. Kaj leaned over, checked the settings. He flipped through a few pages of A.M.'s notebook. They were looking for a pattern: arrows, snippets of sentences. There weren't many notes, but at the back, on the edge of the cover, someone had marked the four pinion positions in pencil: silence, breath, dip, return. The ring was stuck next to the breath. - 'Let's give immersion,' Kaj suggested. He didn't ask if it was sensible. None of them cared. They moved the gears a millimetre at a time. Each click penetrated their fingers, right down to the bone. The moment they hit the dip marker, the fog behind the glass did not descend, but parted, as if someone had pushed it in with their knee. They heard a low, soft tone, so low that it was more felt than heard. Through the lens they were no longer looking at the usual horizon. The air became thick, as if cool water had replaced the oxygen in it. - 'Lena,' said Kaj, and in his voice for the first time there was not only enthusiasm but also caution. - 'There... that's not a reflection. At the edge of the view, where the wave was cut by the remains of the foam, a spot darkened. Then lines appeared - straight as if drawn in pencil - and in them a stirring. Something was growing, though it wasn't zooming in like an ordinary object. It was more as if space itself was bulging. The lens was eating fog and visibility. The lantern breathed faster. The compass on the floor jumped and with a crash the needle hit the metal. Lena placed her hand on the cool glass. Her fingers went slightly numb, but she did not withdraw them. Inside she saw a path of black slabs, wide, smooth, glistening with moisture. The slabs had not been here before, yet they formed something familiar: a staircase. Only not down the rock. Down ... where? Under the water? Under the mist? To the city on the other side of the horizon line? Kaj involuntarily squeezed her shoulder. - Can you feel it? She felt. As if something on the other side, very close by, had moved its hand across the same sheet of glass. As if the skin of the glass had nerves. An A sound ran through her teeth. On the inside of the lens, condensed moisture formed streaks that resembled letters for a second. Lena blinked, trying to catch the meaning. A new note was enough. E. A few digits. Like a fragment of an address. - If we play E, we'll see more,' she muttered. - 'Or something we can't name will come in here,' Kaj said. Despite his words, his thumb stopped millimetres above the slider in the app. The mist trembled. A shadow flashed on the other side of the stairs, and then another, as if someone had stood in the light for a moment and stepped back. The air thickened so that every intake of it into your lungs was like a gulp of very cold water. Outside, the seagulls broke into flight, screamed and fell silent, as if something had silenced them in one movement. - 'Lena,' said Kaj for the second time, but now his voice was quieter and his eyes were wide, as when something suddenly happens in an experiment that even the equations had not predicted. - 'Do you hear that? She heard it. Someone - or something - knocked from inside. Three soft, sure knocks, like on a door that had waited a long time.