Rain washed the windows of the old depot at the end of Rzemieślnicza Street, drawing crooked lines on the panes, as if someone was correcting a map with their finger. Hall C, the largest of the three, stood dark and deaf, but inside it retained the warmth of the day: the smell of grease, dust and heated metal. The tall glass roofs tottered in the wind, and leaves floated in the trickles of water lit by lanterns. Lena Nowicka knew the building better than most of the inhabitants. After school she used to help Mrs Rose in the city archive, which had been moved to the side wing of the depot for a year. There were things in cardboard boxes that no one had time for: minutes from old council sessions, broken seals, photographs from the electrification epic. And boxes without labels, the best ones. It was in one such box, between a ragged cover and a bunch of rusty keys, that Lena found a disc the size of her hand. Brass, heavy, smooth from the touch of ancient fingers. The edge was stamped with miniature letters: ASTROGLIF. Thin lines were engraved on the front, thick as a spider's web. They were constellations - at least that's what she thought - but arranged differently than in a school sky atlas. On the back of the disc was stuck a small rotating arrow and something like a transparent stone that shimmered with colours reminiscent of petrol on a puddle. When she first lifted the Astroglyph under the lamp, a light ran through it from underneath, as if it had collected the glare and cast it in another direction. The puddles on the floor trembled in tiny waves. Lena withdrew her hand, swallowed her saliva and laughed - half from nerves, half from delight. She knew she should warn Mrs Rose, return the find, describe it in her acquisitions notebook. But she also knew that if she put it down now, someone else would be the first to ask him the question that stuck out on his tongue, "What are you for?" In the evening, sitting with her cousin brother on a wall by the river, she took the puck out of her backpack. Michael was a year older, looked as if he was always contemplating a parallel plan, and almost nothing surprised him. He painted murals and knew more about physics than some teachers. - 'This is no ordinary medallion,' she said, giving him an Astroglyph. - Look at the water. The arrow on the rim jumped one line. Michael held the disc above the surface of the river, on which the lights of the promenade were reflected. The stone in the centre came alive with the kind of cold glow that stars have in winter, and merged in a thin line with the reflections of the lights, as if the river were a conduit. Somewhere far away a ship's siren moaned. - An electromagnet? - He muttered. - Or something to do with interference... Except that nothing was powering up. - He touched the arrow with his fingernail. - And the front? It's a plan of the sky. Or a city plan, only on a different scale. See? These lines line up like our streets at City Hall. Lena saw. If you turn the disc over and spread your gaze, the stars arranged themselves in a grid like streets. If you slide it down, the streets arranged themselves into constellations. Suddenly a whisper from her grandmother Halina flashed through her memory: "Not everything that leads has clues". At home, she couldn't fall asleep. Through the window she watched the clouds stretched like nappies on strings. Finally she got up, put on her shoes and jacket, grabbed a torch and Astroglyph. She texted Michael three words: "Hall C. Now?". He replied: "Like a breath." That meant: I'm already running. The depot at night was like a space between two thoughts: almost empty, but tense. The gate huddled against the wall looked closed, but when Lena pulled the puck closer, the arrow popped and the stone glowed pure white. The rusty padlock clicked as quietly as if it had been waiting for this sound for a long time. Michael whistled soundlessly. - 'Don't ask if it's legal,' she warned him. - 'I'm not asking. I'm asking whether to record. - Come in first. Hall C welcomed them with coolness and shade. Between the tracks stood quiet carriages, models from half a century ago, with wooden benches and brass handrails. Their paint was cracked like tree bark, the directional signs faded. In the corner of the hall, under a clock with black numbers, lay an unrolled map of the city, so old that the paper resembled a dry leaf. Lena accidentally put her foot on it. - 'Look,' she whispered. - There should be three tracks here, but there is a fourth. - She pointed to a graphite line, running separately, without a signature. - Track zero. - It's not on the online plans,' Michael replied, already tapping something on his phone. - Nor in any documents from last year. - He raised his head. - But it's here. - He nodded with his chin towards the depths of the hall. In front of them, between two halogen spots of light, stretched a narrow, even line of gleaming steel. It was not rusted like the others. It seemed to have been recently poured with rain, although the roof over it was whole. Lena placed the tip of her shoe on it. She felt a gentle pulsing under the skin of her foot, as if someone were playing a very quiet melody on a string. She took out the Astroglyph. The lines on the front lit up with the colour of starry ice. The arrow made half a turn. The air trembled and dust particles began to swim horizontally, like fish in the middle of the day. Michael stood beside her, holding the torch so as not to shine directly. - Really? - He asked silently with a look. She answered him with the same. Something changed in the silence. The echo of their breaths returned on the other side, as if the hall had gained depth. Then they heard a bell. Not the usual warning one, short and metallic. This sound was soft, almost whispered, and yet every bit of skin on Lena's arms twitched. Out of the darkness emerged a tram that had not been standing there a moment before. Sleek, narrow, gleaming with something that wasn't paint. On the board, instead of a number, a sign flashed: "Stop: Between". - What's this... - Michal lost his words. - Lena, I... Lena's hands were slippery with moisture. She felt the disc in her fingers grow warmer. On the edge, where the letters were engraved, tiny luminescent dots appeared, arranging themselves in a rhythm, as if counting down. 10. 9. 8. They weren't numbers directly, but she understood it as clearly as if someone was whispering right next to her ear: "Right away." The water oozing from the roof began to flow differently - it did not fall, but hovered over the zero track, forming a thin, vibrating sheet of steam. The tram mussed it sideways, soaking nothing, as if its skin was a promise of dryness. The door slid open with a hiss. A chill blew from inside, but not unpleasantly; it was reminiscent of a night at the lake, when you stand up to your ankles in the water and feel the stones through your soles. On the floor, just at the edge, a piece of paper trembled. It flew up and fell by Lena's foot. She picked it up mechanically. It was a ticket - made of paper so thin that it was almost transparent, with an embossed brass frame. In the middle, in fine print, stood her name and the date: today's day. The time? Now. - It's some kind of installation. Or a prank of the city - Michal tried to sound reasonable, but his voice had too high a timbre. - Cameras? - he looked around, but instead of cameras he only saw his breath in short feathers of steam. In the depths of the tram someone moved a curtain. Or was it just a reflex? Lena had the impression that there was a shadow sitting behind the Venetian glass that had no outline but had the patience of a tree. The clock above the city map reached the full hour and rang a single bell, as if the interior of the hall were a cage for that single tone. The arrow on the Astroglyph twitched one last time and stopped, pointing precisely at track zero. - 'Lena,' Michael said quietly. - 'If it's a one-off, it'll be gone in a minute. And if it's not... - He paused. Then the lamps near the ceiling flicked on and off, one by one, leaving only a blue glow emanating from the disc and a milky glow around the tram. A warmth spread under Lena's feet. The puck in her hand, as if alive, slipped and hovered in the air an inch above the track, spinning slowly. The vehicle door widened a finger more, invitingly. From deep inside came something that might have been a breath. Or the whisper of two invisible wheels. Just behind them there was a slight metallic click, as if someone had closed a bolt from the darkness. Michal turned his head away. Lena didn't dare. She was looking at the glittering ticket in her hand and at the door, which seemed to be near and far at the same time, when suddenly the glow inside the tram began to pulsate, like a heart just before a sprint.