Fog crept into the courtyard like the slow breath of the city. On the other side of the gate, the arched windows of the former bathhouse shone with a milky glow; it now housed the City Sounds Archive, a place where the silence was sometimes as thick as the tapes on the metal reels. Lena brought a thermos of tea to her lips, pushed open the heavy door and slipped inside. The smell of dust, emulsion and long-dried soap hit her with a familiar wave. "Good night, Ms Leno," nodded Janek, a security guard with a soft voice and hands so large that the keycards looked like carousel tickets in them. A faint hum of the band, interspersed with short crackles, came from the radio at his desk. "Good night. Peaceful rounds," she replied and took the entry book from him. She signed her name, adding a tiny note next to her name out of impulse - a gesture that had been with her since her internship. The corridor leading to Warehouse A was cool and long, as if made of sheer half-shadow. The neon sign above the door to the studio flicked twice before startling into full light. Lena switched on the main power supply and then the lamps in the 1960s bookshelf, where familiar boxes the colour of faded cream smiled at her. Everything she touched she put down with tenderness: carbon paper, a linen cloth, a duster brush, a packet of cotton gloves. On the desk lay a package she didn't remember from yesterday. Grey paper, red string tied neatly, as if it were a packet of sweets from her grandfather. There was no sender - just a short note in blue ink: "For personal use: Lena W." She tore off the string, unfolded the paper. Inside rested a spool so well-preserved that the paper label still clung to the silky edges. "Line 0 - control crossing - 31 X." The first two digits of the year were blurred, the rest - "74" - legible. Lena lifted the tape into the lamplight. Strong, heavy plastic, characteristic of the end of the ironhead era. The smell of magnetic media filled the air with a pungent, metallic note. "Which cabinet... trams, trams..." she muttered under her breath, gliding her finger through the folders in the catalogue. A manuscript index, numbered in the fine, even handwriting of Mrs Wieslawa, the custodian who retired twenty years ago. "Line 0" did not appear in any inventory. So Lena reached for the thick, cloth-bound receipts journal. She turned page after page. 1974: October. It reads: "31 X - accepted: track test - night - no authors, no signature". Underneath the index in small writing was added, in another hand: "route decommissioned 1975, does not run". Outside, not a trace of the tracks remained after the asphalt. The street beneath the archive's windows had been turned into a cycle path, and the former traction pole was used as a ladder for a wild vine. Lena smiled at her own memory - her grandmother had once told her about the 'zero' bell, which sounded different from all the others because the motormen had a personal relationship to it. "A bell like a sigil," her grandmother used to say, "smaller, but harder in voice." "Janek?" Lena poked her head out of the studio. The security guard wasn't in the reception area; he had left his coat spread out on the chair, and the radio phone murmured a draughty, muffled s-s-s. The silence grew even thicker. She moved the tape to Studer, an old, heavy scroll recorder that silenced her on a par with stroking an old cat. She removed the glass cover, inserted the spool, ran the tape through the reels and head, reached for the headphones with her other hand. She turned the potentiometer down to the usual night listening level, pressed 'Play'. First came a safe, even carrier hum, and then - as if someone had opened a window in an unfamiliar room - the sounds of another hour of the city broke in. The metallic crunch of evening bins, drops on the gutters, distant footsteps on the pavement, a single whistle. And then, finally, this: the rasp of heavy steel, a protracted groan, followed immediately by the clap of a bell. It didn't carry the echo of those modern, harsh buzzers from warning signals. It was short, emphatic, like a confirmation that the wheels had once again touched something that remembered them. Lena closed her eyelids. She was sitting in a well-lit studio, but for a split second she had the impression of the chill that goes from an open door as autumn creeps in from the corridor. The motorman - a man's voice, slightly hoarse - clearly spoke a message from years ago: "Please move away from the edge. Line 0. Control crossing. No passengers." "Great," Lena whispered. She turned the dials, wrote down the shot number and time. She wanted to compare the reverberation later with the plan of the station that, if it wasn't a joke, the vehicle had passed. Then she heard something even quieter, like the sliding of a fingernail over a microscopic scratch: "Lena." She opened her eyes. The sound could have been a coincidence: the sum of the noise, the crackle and her mind chasing patterns. She pulled the recording back a few seconds, listened in. A metallic wave, the air, her breath in the cabin. Nothing. And then - elsewhere in the tape - the same thing. "Lena." Not a whisper, rather an exhalation with a barely marked 'n', as if someone was trying to pronounce a foreign name with a tongue accustomed to other voices. "Janek?" she called out louder, removing her headphones. "Do you hear anything on the radio?" All that answered her was the wheezing of the old lift behind the wall and the knocking of rare water against the windowsill. She reached for her diary. She opened it to 1975, then 1980, then 1990. In each October, someone with the same even handwriting added small annotations next to the '0 line': "tape completed", "another control pass", "no revision number". Mrs Wieslawa's handwriting, no doubt - except that she had long lived in a cottage outside the city and grown dahlias. The traffic on the street had quietened down. The fog thickened, clinging to the windows as if someone had smeared them with milk. Lena perched another roll of papers on top of her, but her hands suddenly became restless, she felt a gentle shiver that had nothing to do with the cold. She turned back to Studer. The motorist's voice sounded closer now, as if the cab was right next to the microphone: "Test run. Interchange not available. Next stop...". At this point the tape rustled, as if someone had touched it with a finger. Janek's radio beeped more sharply than usual. Lena ran up, pressed the button. "Janek? Are you there?" A breath emerged from the crackle, then the scrabble of boots. "Mrs Lena... Do you hear that? In the courtyard... the bell..." The voice broke off as if with scissors. A steady, high-pitched screech came from the radio and disappeared suddenly, leaving a painful gap in her ears. Something fell in the studio that resembled a lack of time. The clock on the wall - an old one with a spherical glass and faded numerals - pointed to midnight and stopped, although Lena knew that the mechanism had been replaced last month. In that motionless second, she felt the tape on the reel vibrate slightly, although the drive was stopped. A heavy fire door opened in the corridor, just as a draught opens it when someone rushes down the stairs. Lena stepped out of the studio, stood on the soft carpet of the connecting room. The fog came in a thin trickle under the threshold, and with it the smell of wet steel. On a table against the wall lay a notebook with patrol logos; a strip of damp appeared on its cover, like a smudge of a hand. And on the sheet with today's date, in the "remarks" space, someone had written in thin, even handwriting - identical to the receipts log -: "Passage 00:15. Passenger: Lena W." Her heart pounded harder, as if it had found inattention in her chest and decided to take advantage of it. "Good joke, Janek," she muttered, although she knew full well that Janek was typing like a first-grade lezzie in block letters. She grabbed her phone, reflexively tracing the call icon. The screen lit up with a faint light and immediately went dark; "No network", even though the archive usually had coverage like magic. Back in the studio, the tape moved without her touching it. The reel, as if spellbound, spun at an even pace, and the head fed a sound so vivid into the headphones that Lena reflexively took half a step back. "Waterfront stop," announced the same male voice, this time with a peculiar softness, as if he were speaking to someone he didn't want to frighten away. "Watch your step." "There is no such street," Lena whispered, although memory - a stubborn animal - immediately put forward the image of old plans on which the Vistula had the escarpment drawn differently, and the former Nadbrzeżna did indeed run where the houses and car park are today. On the desk, next to a pencil and an anti-static strip, now lay an object that had not been there before: a parchment old tram ticket, as thin as a moth's wing. Two tiny punch holes formed the number "0". On the back someone had written in pencil: "Are you getting on? 00:15". The hour on the clock still stood. But somewhere beyond the walls of the bathroom brick, the metal rang again: the bell, once, twice, a third time - short, hard claps. Lena walked over to the window. The fog curdled against the pavement like foam, but in the midst of the whiteness, for a split second, she saw something impossible: a thin, dark line glinting under the light of the lantern, as if the asphalt had moved away for a moment, revealing two parallel tracks. The Iranian carpet of fog shifted again and everything disappeared. Instead, a moving strip of light appeared on the wall of the studio, wandering as a spotlight moving across the glass panes wanders. Studer murmured more deeply, as if someone had energised him. A cool blast sounded in the headphones, then the creak of a door, followed immediately by a familiar, sparing sound: "Door close." Outside, the bell answered it once more, with a shorter, more emphatic clap. Lena felt the leather watch strap soften in her hand. Her fingers found the window lock by themselves. She pulled lightly until the mechanism made that distinctive sound, soft and disconcerting, like breathing right on her ear....