Autumn always came a little earlier in Nadjeziorno than elsewhere. Fog hung over the water like a heavy curtain, and chestnut leaves rustled on the cobbles around the Konarski High School, a red-brick building that remembered more than anyone wanted to admit. Towering over everything was the clock tower, so old that no one tried to repair it anymore - at least officially. Lena sat on the windowsill of her room with her feet propped against the radiator and headphones on her ears. She was mixing recordings for a school podcast when she heard it for the first time: a faint, metallic tone sandwiched between the crackle of sparrows and the clatter of wheels on her ankle. A single sound, as if someone had struck a forgotten gong from the other world. She flicked her hair away from her face and undid the recording. The amplitude graph was clear, narrow as a needle. The recording time displayed 01:13. - Again? - she muttered to herself. This 'again' took its cue from the night before a week ago, when the same tone rolled through her recorder, set up by the open window. Back then she'd blamed it on radio noise. Today she couldn't. The phone screen flared. "Got it?" - Maks wrote - "I'm awake. SDR caught in spades at 01:13, direction: tower." Lena immediately called him. - How much confidence do you have? - She asked without greeting. - More than I like to admit. I set up the antenna on the roof of the boarding house. The bandwidth was like a razor blade. It was coming out of there - from above. And it wasn't just the hum of a transformer. - You know that if someone's broadcasting it, they're either making fun of us or calling out - Lena paused, listening to the silence on the other side - for something else. - 'Maybe both,' Maks replied after a moment, 'We're meeting tomorrow. Library. I have something else. The next day the thin sun floated over the courtyard like undrinkable tea. The library smelled of dust, ink and old atlases, which Mrs Crow flipped through with pious patience. Lena entered, taking the headphones off her neck. Maks was already waiting between the bookcases with his hands in the pockets of his sweatshirt, impatient, with the gleam in his eyes that appeared in him whenever things started to come together in a jigsaw puzzle. - 'Look,' he said, placing a crumpled envelope on the table. - I got it this morning. No stamp, someone should have dropped it straight into my mailbox. Inside... He slid a small, heavy key on a brass ring out onto the table. On the tin near the key someone had engraved: 1903. - That's not all," he added. - There was also a leaf. Briefly: 'Look into the twilight, not the light. The north is not alone. - L." - L? - Lena raised an eyebrow. - Do you know such a person? - Not the kind who leaves old keys - Maks shrugged his shoulders. - Does that tell you something? Lena felt her teeth clench coldly inside. Her grandfather, Leonard, had been dead for years, but his initials L.K. were on the back of a notebook she had kept on her shelf since she was a child. He used to be a physicist and taught at Konarski. On some of the pages he drew the clock tower with such meticulous detail, as if there were patterns playing within its walls that only he could hear. - 'Maybe it's nothing,' she said, although she didn't believe in 'nothing'. - But 1903... the vintage of the rebuilding of the wing with the physics room. And apparently something else was built then. Underneath. - Underneath the school? - whispered Maks, as if Mrs Crow could read lips. - Is there a map? They approached a display case with a plan of the building. On the 1968 plan the corridors went down, but a section was marred with stamps, as if someone had sloppily hidden something with a marker. The contemporary plan, hanging next to it, no longer included any cellars apart from the boiler room. - 'Twilight,' muttered Lena, looking at the glass of the display case. - Shadows are where the light doesn't reach. If there is something 'in between' the official plan and the old one.... Machinistically she moved her hand over the frame of the display case. The wood near the left edge was gently slipped, as if someone had touched there often. She propped the corner and felt for a crack. The plan let itself slide out like a drawer. Behind the glass, beneath the map, lay another - a thinner, faded photograph of the plan on transparent tracing paper. - Look,' she hissed. - 'There's a corridor here that's not on either of the two plans. It goes under the library. And it ends with a room marked 'A-13'. - 'Thirteen,' smiled Maks nervously, 'I think we like that number today. Mrs Crow lifted her gaze from above the counter. Lena quickly slid the carbon paper back in. They didn't want to explain too much. Mrs Wrona had a knack for questions. In the evening, when the school was emptying, they returned. Lena risked being locked inside, but Konarski's walls hid too much to let go. They knew where to look: a bookcase of pre-war atlases stood at the end of the row, by a dusty window. With a joint effort, they pushed it back a few centimetres. It creaked in such a way that Lena involuntarily held her breath. Behind the bookcase was a wall. And something more: a vertical strip of bricks that did not match in shade. As she ran her hands over them, one of the bricks gave way. Behind it gleamed a castle, so old as to be improbable. - 1903 - whispered Maks and handed her the key. It fitted perfectly. The lock rattled, the darkness sizzled like paper in a flame, and a section of the wall swung open slightly. Behind it began a narrow, steep staircase. It smelled of chalk, rust and dry lavender, as if someone had hung bags here long ago that still held a trace of the scent. - Do you have a torch? - Lena asked. - I have two - he took out of his rucksack. - And a recorder. I set it to record. They descended slowly, counting the steps in a whisper. Thirty-two. Thirty-three. After forty-five, the staircase broke off into a narrow corridor with a low vaulted ceiling. Pipes trailed below the ceiling like metal veins. Every few metres, porcelain lamps hung on the wall, unplugged for years. On the first door on the left someone had once pasted the letter A. Underneath, almost starting, Lena saw the thin scratches that someone had made with a compass or a blade: the outlines of a clock face with the hands set to 01:13. - 'Who did that? - whispered Maks. - 'Someone who knew we'd be watching,' she replied, feeling the hairs on the back of her neck stand up. They walked on. The door was locked with keys they didn't have. The corridor turned gently, and then they heard it: a very quiet rumbling, as if sucked through the walls, rhythmic, almost like a heartbeat. The recorder responded: a line flashed on the screen. Lena raised it higher, the microphone almost touching the plaster. - It won't tell me where it's coming from,' she murmured. - The direction blurred. As if it was everywhere. - Or as if something is listening to us from here - added Maks quietly and immediately regretted it. When they reached the end of the corridor, they saw a steel door unlike any other. It had a round window as thick as the trunk of an old oak tree, sealed with black rubber. Next to it, on a plaque, polished long ago by the hands of many people, they read a faded inscription: ARCHIVE A-13. - 'This is impossible,' Lena said, although she knew she had long since stopped trusting the word. The window was foggy on the inside, as if a different kind of weather was behind it. Lena put her hand to it. The chill bit through her skin to the bone. On the other side, as if for an answer, there was a mark - from inside the window, someone had run a finger over the glass, revealing single letters in a translucent haze. Inverted, but still legible: N I E S A M I. Lena withdrew her hand so violently that she almost dropped the recorder. At the same moment, the light of her torch faltered and went out. Maks's torch whirred, dimmed, flared again, as if the batteries were afraid of what was in front of them. - It must have slipped,' he muttered, but his voice trembled. From deep behind the door came a soft sound, like a film projector turning on somewhere far away. Above their heads, something walked along the pipes - heavy, bold, with unhurried intent. In the silence following this step, Lena heard the echo of her own breathing and a stray tick-tock, though no clock walked here. - Do you hear? - She asked and pressed her ear to the cold metal. A vibration passed through her like a word in another language. Maks nodded and pointed with his chin at the lock. It was not a key lock, but an old mechanism with four knobs, each with letters of the alphabet. Someone had long ago stuck a short sentence above them: "Look into the twilight, not the light". - There's that quote again," he whispered. - You're thinking... - That it's... - Lena swallowed her saliva. - That someone is leading us here step by step. Her phone vibrated in her pocket. The screen brightened for a second and immediately went dark. No network. No time: the clock on the display vibrated, flashed 01:13 and went off for good. - 'No,' she said into the silence. - 'It's nine o'clock. I would know. Someone above them moved again. This time they heard it more clearly: a creak, a clatter, a slow descent down the stairs, as if an old shoe were sliding across the floor. Maks trembled, but straightened up and put his fingers to the first knob. Lena took a deep breath and leaned over the mechanism, trying to piece together all the hints that had been left in their path. And then, on the other side of the window, in the mist, apart from the letters, there appeared the outline of someone standing very close to the glass, as if only millimetres separated their gazes. The door squeaked quietly, as if trying to anticipate what would happen when the dials were set to the right word.