The hill above the town looked like a dark island emerging from a sea of blocks. An observatory stood on it - closed for years, with a black, cracked dome resembling the closed eyelids of a sleeping giant. The road to the gate led along a narrow strip of crumbled asphalt, where the streetlights had long since ceased to work. On the mesh of the fence someone had spray-painted: "DO NOT ENTER - OSUWISE", and someone else had added: "YOU'RE GOING IN ANYWAY". Lena snagged her backpack on the wire and the metal squeaked, announcing their presence to all the hill ghosts. Instinctively, she looked back at the lights of the town, where shops were still selling hurried dinners and the platform was silent after the last train had departed. Oscar, always half a step ahead of her, was already challenging the padlock at the side gate. - Are you sure? - he whispered, although there was no one around except the wind and two frisky blackbirds. Lena nodded. In her coat pocket she felt the weight of a brass key. She had found it a week ago in her grandmother's flat, slipped into the cracked cover of a yellowed notebook. On the cover was a drawing of the observatory dome and a date from three decades ago. Next to it, in her grandmother's handwriting: "The night when the Arrow cuts the Crown - don't be late". The key had three points engraved on it and a thin line like a constellation. Lena wondered how many times her grandmother had taken it in her hand before she passed away, and why she never mentioned it. The padlock gave way with a groan. Inside, it smelled of dust, iron and a chill that knew no calendar. The stairs leading up to the terrace creaked underfoot and the railings were viscously rusty. - 'When you told me there was something here, I thought you meant, I don't know... a telescope to sell to a collector,' muttered Oskar, leaning his torch against his shoulder. - Not that we're going to spin the dome until the screws fly out. - No one's telling you to spin it - replied Lena. - 'But... take a look. In the main room, beneath the dome, a console waited: a panel with rotating dials, dead clocks and a lever larger than a forearm. Dust everywhere, as if stretched by a thin layer of ash. On the left, on a pedestal, the empty frame of a display case was gone. On the right - a large mirror, obscured by a cloth that had once probably been maroon, now faded to an earthy brown. - And what? - Oskar asked. Lena reached into her backpack. She put her grandmother's notebook on the panel. The pages were full of tiny diagrams, smaller numbers and things that resembled sky maps, but different from the school ones - threads and dots were arranged in drawings that she didn't associate with any constellations. Words appeared between the lines: "mirror", "conjunction", "Corona", "Arrow". On one of the front pages, someone had glued a cut-out piece of newspaper with a photograph of the observatory and the caption: "Last night of work - Director Dr Jastrzębski says goodbye to a respected facility". - Is that him? - Oskar pointed with his finger. - Your... - Grandma was his assistant,' Lena replied before he could guess. - She said that they used to look at the sky for so long that sleep stopped bothering them. Then suddenly everything was shut down. 'Ash,' she added unconvincingly, pushing an embossed pocket near the bottom edge of the panel with her finger. The pocket clicked open. Inside, in a brass sleeve, a keyhole waited. Lena slipped the key in and turned it. Somewhere deep it rattled. Above them, the dome seemed to breathe. There was an almost inaudible murmur in the room, like the distant sound of the sea. For a moment it seemed as if the floor moved a hair. - A resonance? - Oskar squinted. - Or the wind. - Or the train - Lena smiled nervously. From downstairs, from the station, came a metallic clatter that grew like a whisper and then suddenly fell silent. At the same moment, her wrist watch, inherited from her grandmother, vibrated and... stopped. The hands stopped at 21:17, humming quietly, as if stuck in a place where they didn't belong. - Well, nice - sighed Oskar. - The watchmaker will be delighted. Lena removed the gowns from the mirror. The fabric, trembling, fell to the floor, scattering clouds of dust. The mirror was no longer a glass that remembered the sky; rather, it resembled a sheet of ice in which past breaths had been frozen. Someone had carved delicate lines and numbers on the frame. A narrow peg glinted at the bottom edge, as if to encourage the pulling of a lever. - There's something here,' she said quietly. - 'See these marks. 'When the Arrow cuts the crown'. Oskar looked around the dome. Along the inner wall was a narrow balcony with knobs, and above it a slider-closed section of the dome that had once revealed the sky for a telescope. Lena stood by the lever. - 'Help me set it up,' she asked. For several minutes they struggled with the mechanism together. The bolts resisted, the cogs creaked, but under the jerks they gave up. The semi-circular opening in the dome opened with a groan. The air from outside rushed in, cool, carrying the smell of decayed leaves. The sky went grey with the week-old dust of the city. High up, almost inconspicuous, hung the Northern Crown, and somewhere beside it, the tiny Arrow, so silent you had to know where to look. - Done - Oskar leaned against the balustrade. - And now what? Waving the key and asking for miracles? - Grandma wrote down the time - Lena pointed to the notebook. - 9:17 p.m. That's... now. - She lifted her gaze to the still second hand of her watch. - It's now or never. She grabbed the lever at the mirror. The metal was cold and sticky. She tensed her muscles. The lever twitched, then gave up, dropping gently. Something inside the mirror burst noiselessly, like a bubble of air in ice. A thin, milky braid spread across the surface and began to swirl in the opposite direction to everything Lena had ever known. At first she thought it was just a reflection from a streetlamp; but the lamps were not lit. - 'It's an optical illusion,' said Oskar with words he wasn't sure about. - Or dampness. - Look carefully - Lena didn't tear her eyes away. - Moisture doesn't make a sky like that. The image in the mirror deepened, took on a light not from here. Gone was the reflection of the dome, their two slender shadows and the reign of dust. What appeared was something that looked like a hollowed-out bay beneath a dark milky shell. The outline of a foreign shore, an arc of rock above the water. Somewhere far, very far away, two bright points hung in the black, clear firmament, too big for stars, too motionless for planes. Lena felt her breath slipping in her throat. Her gaze tracked every movement of light, every whisper of shadow. Underfoot, a strange sensation swept over her, as if the floor were floating, a slight, uncertain vibration that resembled the rocking of a boat by the shore. - 'Impossible,' said Oskar, and for the first time something that was not a joke sounded in his voice. - Do you see the same thing? - 'We see the same thing,' confirmed Lena, although it sounded as if she was talking not to him but to herself from a week ago, when she still thought that her grandmother's keys were for old cupboards, not for opening... whatever it was. The mirror murmured. It was not a sound that could be described; more the sensation of a touch that did not touch. The air above the sheet trembled. Somewhere deep, on that shore, a light shimmered in a shade of green, as if someone in the distance had moved a lantern beneath the rippling water. - Lena - someone said, very clearly. A cold jumped up her spine to the nape of her neck. Reflexively, she turned around, but behind her was only a dome, an empty gallery, an old console. Oskar heard it too - she could see by his face how his jawline tightened. - Who's there? - he called out, but the echo swallowed his voice, spitting it out as something weaker and less convincing. - 'Lena, don't be late,' the voice sounded soft now, familiar. It wasn't her grandmother's voice, although her memory immediately took on that tonic. This one sounded different. Like a phrase that had been said once before, and in a place where it smelled of night and metal. Oskar squeezed her shoulder. - It's... who? - He asked quietly. Lena could not answer. The wind rustled in the open gap of the dome. Outside, the town hummed like a box of cables. Here, inside, time stood nailed to 9.17pm, like a moth to a pin. In Grandma's notebook, right next to the drawing of the dome and the mirror, there was one phrase that kept coming back to her at night all week: "Don't go in alone". The question was: what does 'enter' mean? Into what? And is the sentence, written in the trembling hand of someone who already remembered the world differently, a prohibition or a warning? The mirror became as smooth as water before jumping. The two bright points on that side separated slightly, as if moved by the breath of an invisible wind. A shadow of some kind of structure - a platform? a bridge? drove into the depths of the bay. - and disappeared. For a moment, for a blink, just enough for Lena to feel the heat gathering between her shoulder blades. - 'If that's some kind of projector, it's brilliant,' said Oskar, but without belief. - 'If it's any projector, how does it know my name? - whispered Lena. She stepped a little lower down the step and brought her hand close to the taffrail. The chill hit like the cold breath of a cellar, but there was no glass. There was something that was neither hard nor soft - a resilient surface that bent under her pads, then moved away, as if she didn't want to let it go or... didn't want to let it go. - Lena, what are you doing? - Oskar leaned in next to her. His face in the torchlight was the colour of dark oil. - 'I'm breathing,' she replied mechanically. - And I'm counting. - To how many? - Up to three. Or to ten. Or to the point where it stops being scary. The voice spoke again, calmer than it should have been if it belonged to someone waiting on the other side of anything. She heard a note in it that could not be faked. The one that makes a house recognisable by the footsteps on the staircase. - Lena. Finally. - Can you hear it? - Asked Oskar, without taking his eyes off the rippling surface. - I hear it,' he said. - 'And I don't think it's an echo. The console beeped quietly, as if the old woman was protesting against a draught. The lever moved itself a millimetre, as if under the influence of someone else's hand. Grandma's notebook turned a page, although there was no air movement in the room to explain it. The arrow hovered over the Crown in perfect alignment, as in the drawings. - 'We've got maybe two minutes before the arrangement goes,' whispered Oskar, not sure how he knew this. - 'If it's anything... it's dependent on the sky. - And if it doesn't? - Lena felt her heart pounding in her throat. - What if it's like a lift door about to close? Something touched her hand from the other side. Gently, carefully. Like the hand of someone who doesn't want to panic. It wasn't warm or cold; it was like a memory of warmth and coolness, overlapping into illusion. An electric shiver passed under her skin that had nothing to do with the tension of the installation. - Lena - the voice sounded closer now, almost next to her ear. - 'If you go in, you won't look the same again. Oskar looked at her questioningly. In his eyes she saw the reflection of two worlds at once - the one with the dusty air and the one over there with the light that shouldn't match any of their physics lessons. Before she had time to respond, a thin, pulsating glow ran along the frame of the mirror. The edges of the frame came alive, as if the inside of the room was no longer enough. The bottom of the bay on that side shimmered, and something large moved in the water, like the shadow of a boat, but too flat and too smooth. From the depths came a steady rumble that intensified every second - a sound like the even rhythm of a trajectory, too precise to be random. - Can you hear it? - Oskar asked, but did not wait for an answer as the mirror made a creaking sound, as if the frame could no longer support the alien weight. The glow at the edges grew brighter, the wood under his fingers warmed slowly, and the air around him trembled as if over a cooker. Lena felt that if she let go of the lever now, everything would collapse like a house card that someone had blown the wrong way. If, on the other hand, she held it down, something would happen that she couldn't name or move forward in time to prepare. A rumble, a light, her name - all at once. A shadow leaned out from behind an arch of rock on that side, too human to be a spectre and too distant to be safe. The edges of the mirror lit up with a white line. Something - or someone - began to emerge from the depths, swiftly, urgently, as if time had its fancies on that side too. Lena tightened her fingers on the lever. Her breathing stopped for a second between her ribs, and everything around her narrowed down to the two words she was about to say or swallow. The door was no longer just an image. They were turning into something to walk through....