An autumn wind from the north was shredding the waves off the old harbour at the Birch. Lena, the seventeen-year-old author of the school podcast City of Whispers, was walking along the deserted breakwater with a voice recorder. She was recording the rhythm of the foghorn of the lighthouse when something strange slipped in between the tones. The double tone, like a clumsy whisper, repeated itself exactly three times and then fell silent. At home above her mum's antique shop, Lena rewound the recording and stuck her headphones in deeper. She picked out the sounds - short, long, short - until they formed a familiar rhythm. Her grandfather had taught her the Morse alphabet before he passed away, leaving a drawer full of brass and secrets. Now the signal filed her name and the time: twenty-first thirty, beacon. -Someone's playing, is someone calling me? -she whispered to the empty map shelves. The lighthouse had been closed for years, its light extinguished when the new harbour was built. Oskar wanted to go with Lena, but was swamped by his father's sudden duty in the kitchen. She took a torch, a recorder and an old brass key found in the book The Lighthouse Keeper's Diary. An engraving shone on the key's head: an irregular amber shard and a date from decades ago. The wind carried salt and silence as she pushed open the steel door at the foot of the tower. The lock gave way with a single click, as if the key had been waiting just that night. The interior smelled of dust, oil and something else, metallic like a rusty song. There were maps of the currents hanging on the wall, and underneath them a warning written in chalk from a few days ago. 'Don't open the light if you don't know who you're calling,' proclaimed the cursive, emphatic writing. Lena climbed the winding staircase up to the laterna, where the lens slept beneath the canvas. Waiting on the control table was an envelope with her name on it and a thin strip of photographic film. Inside the envelope was a map of the bay with a red cross and a handwritten note: START WITH SOUND. Lifting the film in front of the phone's light, she saw a blurry silhouette standing on the stairs behind her. An old radio snapped on, the dusty scale glowed green, though the cord was unplugged. -Lena April - said a voice somewhere in the noise - you have a key you shouldn't have. The siren blew from the seaward side otherwise, followed by a lift of sound into the lighthouse itself. Footsteps came from the stairs, timid at first, then more confident, as if someone was counting the steps aloud. Lena squeezed the key, slipped the film into her pocket, and the torch suddenly went out. Just below her feet, someone stopped on the platform, then began to climb.