Mira worked nights in a side reading room of the Cartography Museum, where only the clock and the soft rustling of cards could be heard. On Monday she picked up a senderless package, wrapped in paper with the harbour crest obliterated. Inside lay an atlas bound in linen, heavy, warm as a sun-warmed stone, and a short note: For Mira, who hears the shores. The signature read: aunt Irmina, although the aunt had disappeared when Mira was nine. No one knew where she had sailed off to, and no one spoke of her out loud either. Mira unfolded the atlas and the air shifted like a wave under the board. The maps did not smell of dust, but of salt and tar. On the first page stretched the Outer Waters, dotted with islands without names, and the dotted route ended with a point described: Midnight Gate. The coordinates did not match any layout she knew. The ink silently pulsed on and off, as if the maps were breathing. Mr Roch slid his head in the door and muttered that he was closing in an hour. Mira nodded and tucked the atlas under her desk, though she couldn't stop thinking about it. As midnight struck, the museum grew even quieter. A lamp went out, a flash and then the light again, as if someone had sailed over the ceiling. The smell of salt thickened, and the electronic clock flashed a thirteenth that he couldn't make out. A ribbon woven into the back of the atlas concealed a small iron key, smooth from repeated holding, with an engraving of a wave. Mira fit it into the lock on the narrow door behind the catalogue rack, a door that was usually a dummy wall. The lock sighed, let go, and a colder breath broke into the reading room. Beyond the threshold was a staircase she didn't remember from any plan of the building. The stone steps had edges worn away from droplets and sand, as if the tides themselves had walked on them over the years. From somewhere below came the sound of a bell, muffled as if by water. Mira looked at her phone screen, but there was no range or time, only the twitching icon of a lighthouse. Someone had long ago painted a bowless ship on the wall, and the blank space dragged her gaze like a missing word. She heard a whisper, clear and yet without source: "Don't go alone." She didn't intend to go alone, but she didn't know who to call for help either. Mr Roch had already closed the gate and the rest of the town was asleep, unaware that a chilly trail had opened within the walls. Mira set foot on the first step and felt a slight movement under her sole, as if the stone was adjusting to her step. The atlas unfolded on its own on the tabletop, the pages surpassed one another and stopped at a plan of the city. A tiny lantern shone above the river, which had not been there yesterday. Its pulse matched the flashing of the light. Fine sand settled on the railing and grains formed the letters of her name. Mira leaned over the banister, trying to catch movement in the darkness below the stairs. A chill rose from below and something else, a deep draft of air that carried overheard words. In the porthole to her left, which she had never seen on the stairs, she could see the horizon line shifted by slow currents of stars. She touched the glass; it bent under her finger like the skin of a drum. At that moment footsteps sounded from the depths, sure, steady, coming towards her, and on the other side of the glass someone knocked once, a second, a third time.