Lena adjusted the strap of her backpack, rubbed her glasses and looked at the flashing screen of her phone. An unknown number had just sent an audio file, named with a surprisingly simple word: Woodpecker. Oskar, the best ham radio operator in high school, perked up when he heard a clatter in the rhythm. - 'Morse,' he said briefly, already switching on his old, worn-out handheld radio. On the recording, a metallic bird was drilling into the wood, laying down cold dots and dashes. Lena's grandfather had once been a traffic duty officer and sowed legends of frozen tracks. Today the legends came back in numbers: coordinates, a time signal and one word, BRZEZINA. Oskar transcribed the string and then displayed a map with red pixels in the middle of the forest. The old station, closed for years, apparently had a concrete shelter called Corridor Seven. - 'At twenty-three seventeen,' he muttered, 'if it's a joke, it's a very stubborn one. Night was descending fast by the time they reached the platforms covered in pine trees and stiff grass. The windlass was rusty and the station clock stopped at twenty-three, without a minute. The departure board was flashing, although the electricity had apparently not been here for ages. Someone had drawn an arrow and the letter K in chalk, leading under the check-in hall. Oskar touched the railing and his radio beeped, as if something was answering from inside the platform. Under a grate of broken boards they discovered a metal hatch with the number K7 and an anchor embossed on it. There was no padlock, just a fresh band of plastic, cut evenly, like a knife. Lena put her ear to the metal and heard an extremely quiet ticking, like a clock deep. - 'There's air down there,' whispered Oskar, feeling the draught and the chill of the underside of the ground. The phones lost range and the walkie-talkie banged out the word LENA, choppy but not random. They opened the hatch slowly, holding their breath as the hinges groaned like old cables in the cold. The smell of grease and lake water wafted up from the darkness, and then the underfoot steps appeared. Below them stretched a tunnel, and in it, far away, a pink light blinked rhythmically. Lena put on her gloves, grasped the cold rung and looked at Oskar wordlessly. Then the whole platform trembled, and the glow of an invisible train slid across the dark track. An announcement with their names on it, crackling and cold, flowed from the speakers, which were not here. - Can you hear it? - Oskar swallowed his saliva - someone had activated the station just for us. From below there was the sound of water and shifting chains, slow, relentless. The light in the tunnel faded, then flared amber, laying down a familiar sequence of marks. Lena counted the dashes, the dots, the breaths between them, and felt her neck go numb. It wasn't a rescue signal, but a command without hesitation: Come in now.