The moon was full and Pim Sabiston was not in bed. She had a butter knife, a string bag, and one excellent reason. Down below the town, where the black shale slides into the water and turns into a beach of round grey stones, the limpets were fat, the tide was out, and nobody at home had said no. She was eight. She sang the whole way down, because her feet needed something to do.

The shingle was cold through her boots. Pim went along the line of the water, prying limpets off the flat rocks into the bag. One, two, three, and count, her grandmother always said, so your hands know what your head is doing. The water was a pale jade in the moonlight and it lay as still as poured glass. Then her knife went into something hard that was not a rock.

It was a lantern. A brass lantern the size of a birdcage, half full of shingle, with salt crusted white across the glass. On the front, where every lantern on the Ridge Line carries a plaque, there was a flat plate of brass with letters cut into it. Pim tilted it under the moon. The letters were cut deep, but the sea had worn them down to shadows, and she could not read them at all.

Her grandmother had a rule for that, since Pim could walk. You never say a name off a plaque out on the shingle, she said. Down there is no lamp to sign it, and a name said for nothing is a name wasted, and the sea does not give them back. So Pim did not say it. The tide came up, lifted the lantern once, and let it go.

The key Pim wears is a brass lantern shape on a cord, and it hangs at her throat day and night, even in bed. Four hundred steps. Her bag of limpets went first, on the third landing, in a soft grey spill, and she did not go back for it. The lantern was heavier than it looked. Carrying it up, she had to hold it high, because if she held it low the shingle inside it ran to the bottom with a sound like a bad clock, and then all the light in the world would sit in one corner. Above her, the nine lamps of the Ridge Line were going up one by one, small orange people walking out along the cliff.

Neel Ferrin was scrubbing the third post in the rain, a strange thing on a clear night. “Listen —” Neel began, and then changed it. “Go to bed.” Pim held the lantern out where the light could find it. “There is a name on it,” she said. “Only I can’t read it.”

The Lamp House smelled of hot brass and kerosene and a hundred years of trimmed wick ends. A hundred and one lanterns hung on cedar pegs, sorted by name, every plaque polished. Pim set the shingle lantern down on the table, on top of the good ones, and it looked wrong there the way a fish looks wrong out of the water.

Hadren Vole came in off the Ridge Line with his coat open and the rain steaming off him. The white stubble on his jaw had gone the pale green of sea foam, and there was lamp-black in the crease of his right thumb that would never wash out. He looked at the lantern and did not touch it. “That came off the shingle.” “Under the town.” “Under the town,” Pim agreed.

“Why are you up?” “Because there is a moon,” said Pim, rhyming the last two words the way she did with everything, whether or not they matched. He turned the lantern over with two fingers, the way you turn something you do not want to be holding. He worked the salt loose with his thumbnail, wiped the plate on his coat, and did not say the name out loud either. Then he stopped. “Ilsa Trew,” he said, low, to nobody. “Of Blackside.” “Is she in here?”

He looked at the pegs. Pim watched him look at the pegs, and she saw him count them without counting. “She is. Second shelf. The peg with chalk on the underside.”

“Then she has a lantern.” “She has one. She has had one since the Winter of Lost Boats, and she has never been on the Ridge Line, because there are nine and there are always nine. No tenth post can be raised, and that is the shape of it.” “She is in the bay.”

“She is in the bay. She has been on the tide board every night for thirty years with a name and no lamp, because the sea has never once asked for her. The sea quietly stopped charging for her, so nobody has had to pay, so her lantern has had nothing at all to burn for.” “So she washes it up,” she said.

“So she washes it up. Every full moon, in a tide that carries it a little further up each time, until one night it is high enough to be found. And then the next full moon takes it back down.” He set it down. “I have known since I was twenty-two.”

“You have known, and you have not said anything?” “Somebody has to be the one who says it.” “It is the only one I have.” He was looking at the door. “Pim. There is nothing you or I can do for a woman we have never met. A name cannot be added to a lamp. Nine, and always nine. The shape of the ritual is fixed. Only what is paid into it moves, and I will not say out loud a number I have not got the arithmetic for.” “Then somebody pays for her.” Nobody said anything. Rain came off the roof in one long hiss.

“Write this on your hand,” said Hadren Vole. “A lamp is lit when the bearer gives an hour of their own life into it, freely, in their own hand, with a name in their mind. Not an hour you will get back. An hour you are not going to live. Nine lamps costs nine hours between us, and nobody feels it, and everybody gets older.” “I know that.”

“Then you know the next part. It has to be given willingly, by the bearer, and the bearer has to mean it.” He held up his black thumb. “And a child cannot pay. Nobody has the right to take an hour off a child. That is why I made a rule about you: you do not pay. You carry. That is your trade.”

Pim Sabiston thought about that a long time, standing in a warm room with wet boots on a cold floor. The next thing she said was not a rhyme. “Then the sea is not charging for her,” she said, “so we have to.”

She was out of the door and down the steps before he could get a hand on her. She went all the way down, in the dark, and she did not sing once. At the harbour end of the shingle she turned round. The black water was up against the stones with the moon lying flat along it, and Brinehold was asleep three hundred feet above her, with eight small orange flames moving out along the cliff.

She set the lantern down on a flat rock where the wave nearly reached, and took out her butter knife, because there was nothing else to do with her hands. And then she gave an hour of her own life to Ilsa Trew of Blackside, freely, in her own hand, with a name in her mind. It was the smallest hour anybody on that coast had ever paid. And it was the first honest payment the bay had had in thirty years.

The lantern lit. The cut letters in the plaque filled with light the way they do when a lamp is properly lit, and the sea went quiet around her feet, and a mile out on Cormorant Head the ninth lamp burned on as if nothing had ever been wrong. The next full moon, it came up the shingle a little further. Pim was always down there, a small orange figure on a grey beach, with a string bag, a key at her throat, and a jar put by for the month after next. She had a rule now of her own, and it went against everything the Lamp House had ever told her. It was: finish the job.