The rain was soaking into the cobblestones on Garncarska Street, and the tenement smelled of wet brick and dust. When Lena reached the box, an envelope without a stamp fell out of it, with a distinctive dark blue postmark: "12 X 1984, Kraków 1". The paper was surprisingly smooth, as if it had never lain thirty-nine years in someone's drawer. She was caught up in the lift by Mr Szpak, a neighbour in a woollen coat who still remembered the days when the cooker in this tenement was fired by coke. "The light in the cellars is failing again". - he muttered. - "It's better not to go down there in the evening. And please don't annoy Pepik, because lately he's been hissing at the door at the end of the corridor." "On which one?" - Lena asked, and the lift stopped on the third floor with a slight groan. "The ones without a number." - He replied, as if it was the most normal thing in the world, then got out and disappeared behind his green door. Back in the flat, Lena only tore open the envelope after removing her soaked shoes. Inside was a thin sheet of paper, written in the handwriting she knew from yeast recipes and Christmas cards: the handwriting of her grandmother, Lidia. "Lena. If you are reading this, it means the letter arrived on time. Don't go downstairs after dark. If you hear the clock, come back. A room without a number doesn't like visitors." At the bottom, like a signature, there was only the letter "L." Lena, an archivist at the University, was in the habit of responding to the unlikely with order and sources. The next day, during a break from work, she went to the National Archives on Rakowicka Street. In a catalogue of building plans on Garncarska Street, she found a folder with a faded label. The 1939 plan showing the layout of the cellars stopped at the load-bearing wall; someone had added a short line in pencil, long ago, as if the corridor ran even further. A stamp bounced near the margin: "DO NOT SHARE". And on a sheet of administrative correspondence from 1984, she came across a few lines about "installation failure and closure of the technical room (without number) until further notice". No signature, no further explanation. In the evening, the fog was as thick as milk, and the signal of the bell from St Mary's Church spilled over the rooftops. Lena slipped the torch into her coat pocket. Pepik, Mr Szpak's black and white cat, crossed her path at the bottom of the stairs, hesitated and disappeared as she opened the steel door to the cellars. The stench of paraffin, rust and old laundry rose in a gentle wave. The bulb at the entrance flickered, but the torchlight expertly pierced the darkness. Lena counted her steps: seven to the corridor turnout, fourteen to the metal grating, nineteen to her cubicle. At twenty-three, she stopped at a cool drop that fell on her hand from the ceiling - though the ceiling was dry. Off to the side, behind the tiled box, a brick in the wall stood out. Lena slipped her nails in and moved it gently; the brick came out without resistance, and something flat waited behind it in the gap. She pulled out a Polaroid. The photograph showed the same corridor, the same stains on the plaster. At the end - a door. Smooth, as if freshly painted. No plaque, no number. On the back someone had written in pencil: "Point eight." Lena's watch showed 7:57 p.m. She felt a tight, uncomfortable dryness rise in her throat. Is this stupid? - she thought. - It probably is. Yet her hands were already directing the torchlight to the end of the corridor. The door that Pepik knew and that Mr Szpak had muttered about was right in front of her. The paint on them glistened under the light, scratched at the edges. The handle - tarnished brass - was cool. 7:59 p.m. A soft ticking came to her from deep behind the wood. Not like the old clocks that chop the air with heavy metal, more like a discreet, elegant 'tick', patched together with silence. With each beat, she felt more clearly that it wasn't coming from a pipe, not from a wire, but from somewhere on the other side of the door. 8 p.m. The ticking cut off as if someone had taken the needle off the record. At the same instant, something on that side moved quietly, and then came a sound that could not be mistaken for anything else: a short, mechanical click. Someone from inside had just turned the lock.