The evening train to Ustrzyki was spinning through wet valleys, and Lena was counting bridges. She was nineteen years old and had a rucksack full of botany notes, as she was starting her internship at the national park tomorrow. The wagon was almost empty, smelling of old wood and tea in a paper cup. Under the seat, Lena found a pressed fern in a worn notebook, and underneath it a sketch map of the line, with a dot by the station Zawój. Someone had annotated with a thin pencil: "Don't get off at Zawoj". Outside, the fog was thickening, the windows were getting milky, and the lights in the carriage flickered once and again. From under the floor came a three-part clatter, like a rhythm that no one was pounding out. Lena glanced at her phone: no reception, the clock was stuck on the same minute. As she raised her notebook to the light, the dot on the map seemed to spill out into a blur, growing darker and darker. Outside the window, a rusty sign flashed by with the letters ZAWÓJ, although the train was not slowing down. - Can you hear it too? - asked a boy from a neighbouring compartment, leaning against the doorframe. He introduced himself: Bartek, a geology student, returning from a field internship and knew these tracks like the lines on his hand. He smiled briefly, but his eyes were alert, as if he was counting every tap. - This rhythm is here every summer. They say it's the viaduct groaning. At that moment, the door to the vestibule bolted on its own and the speaker in the ceiling rumbled with silence. On the fogged glass right next to their heads, letters surfaced as if drawn with a finger from the outside: "RETURN". Lena held her breath as the wagon rolled only forward. In a notebook between the pages rustled an envelope she had not seen before, addressed: "Passenger, seat 12". Inside lay a small brass key with a tin on which someone had engraved the word "Schron". - Shelter? - hissed Bartek, but Lena felt the metal was warm, as if someone's hand had just let go of it. They decided to find the conductor in the last carriage before the train entered the tunnel under Otryt. The corridor was drowning in emergency red, and an unsecured hanger swayed loosely underfoot. Footsteps sounded behind them, regular and soft, but when they turned around it was empty, only the light swaying the shadows. The train suddenly slowed unannounced, metal whined, and somewhere far away a draught rumbled. At the end they came across the conductor's cap, still warm, and a trail of wet soles leading to a service door with a sign saying 'Do not open while moving'. From behind the door came the same tapping three times, followed by a whisper that knew her name: "Lena.... open." Her fingers slid the key into the lock by itself; it fit all too perfectly. The latch gave way with a dry click and the door swung back a hand's width, letting out a stream of cool air that smelled of wet leaves. Bartek squeezed her shoulder and the rhythm repeated itself right next to her, as if someone was standing on the other side waiting.