Last Christmas a mermaid died in the school swimming pool. It was only a small pool, built up at the sides with wooden panels, more like a tank for training children in. That meant it froze over very easily, but a mermaid couldn’t know that. It stood in a courtyard in the shadow of the school, and the sun reached it only at rare intervals.

Behind it lurked a stone and sulking outhouse, pebbledash walls lashed together with a corrugated plastic roof. In its damp darkness the children undressed, and tripped, and snapped tight, powdered rubber caps over their skulls. Under its benches something black grew wetly out towards them. It was the hut that Freya hated most of all.

Miss Wallace had caught Archie Dorrick from Upper Third belting down the corridor but she hadn’t told him off, not properly, just asked him why he needed to be rushing so quick. He said there was a mermaid dead in the pool, that it must have happened in the holidays, and Miss Wallace was so interested that she didn’t ask Archie why he had been down there on his own, which was definitely cigarettes.

Miss Wallace was young and pretty and was allowed to wear any jumper she liked, unlike Freya, who was a pupil and had to wear a plain grey one like everybody else. Miss Wallace also had colourful bracelets on her arms and hair that rose up above her head and fanned out like branches. When she moved they swayed about her; the bracelets and the hair both. In the older years they had a teacher for English and a teacher for history and a teacher for comparative mythography, but Freya was only nine so Miss Wallace was her everything teacher, and she needed no other.

Freya’s last teacher had been Mr Heagerty, who had folded himself into a corner of the classroom, spiderlike, and spoke to them only in riddles. His interest in the outside world was oblique at best, and he’d never once worn a bracelet or even a colourful tie. For Miss Wallace, the outside world was the whole point, it was something to push both your hands into and wiggle about. That was why Class 7C were allowed to follow her, symmetrical grey cygnets, through the hall and out the fire escape and down the iron stairway that led to the pool with the mermaid in it.

The ice was frozen over most of it, a thin sheet, breakable. One arm punctured the surface, a long, grey-brown javelin that reached up and out and seized around the metal rung of the ladder in a tight fist. Frost followed up it and caught on the trail of fine hairs that sloped along its back. Freya couldn’t see down below the ice, Miss Wallace had them at a distance, she had first dibs on exploration. Freya jostled her way to the front of the group. She knew she had to be as close as was allowed.

Miss Wallace stared down at the mermaid, and her hair quivered, and her breath came out in clouds. Below her the arm was stiff, and quiet, and altogether too close to her throat. In the end it was Juno Clarke who asked the question that held them all close with a ferocious anxiety. Juno asked if Miss Wallace was sure it was really dead, and Miss Wallace said yes, and everyone turned to Juno and sneered at her stupidity.

Then Miss Wallace said “I can prove it,” which was something she said a lot, and she felt around inside her pockets and pulled out her fountain pen. Freya had long watched and desired that pen, it shone bronze and under Miss Wallace’s direction bled blue, looping calligraphy that far outranked Freya’s lumpen hieroglyphs. Miss Wallace took off the lid, and lifted the pen high, and then stuck it deep, deep into the mermaid’s arm.

Later, when Miss Wallace encouraged them to come close, to huddle around and stroke the arm for themselves, to learn what they could from this rare chance, Freya’s finger found the hole the pen had made. Without really meaning to, she dipped it inside, into the cold and sleepy meat. It resisted her, but she felt deeper, she wriggled her finger down to the end of the incision and scratched at the bone. Freya thought to herself that she might be the first person in history to reach inside a mermaid’s arm and scrape their nail across the bone, and in that thought there was no horror, but a realisation that for the first time, in her life of classmates and brothers and older cousins, she had experienced something truly private, something that could not be shared and that belonged to her alone. And Freya understood that there was and would be nothing else she desired as she desired the mermaid, and she knew what she had to do next.

First, before the science lesson had begun, Miss Wallace came back across the courtyard and told 7C that she had an important question. Her face was suddenly very serious, and she went round in turn and asked if any of them had put the mermaid there, and Freya said no and Tim said no and Fergus said no even though if anybody had put it there, it would definitely have been him. Marybeth asked Miss Wallace how the mermaid had got into the pool, since it hadn’t been any of them, and although the class glowered at her automatically, Freya felt it was a Good Question. Miss Wallace said that if it hadn’t been anybody in another class, then maybe it had crawled out of an estuary and dragged itself inland. Mermaids could manage that, for short distances. Maybe it had seen the pool and thought in its animal mind to refresh itself. It would have heaved its long body up, over the wooden side, and only when it hit the water would it have realised its mistake.

There were a lot of questions now; the pack had grown both curious and tolerant. Jason wanted to know if it was a boy mermaid or a girl mermaid. Miss Wallace said she couldn’t tell because of the ice, but that if the tail was big and squashy that might mean it was full of babies. Joanna Fitch asked if it was saltwater or freshwater, and Miss Wallace reminded her that mermaids were freshwater, that if it had been saltwater then it would have been a dead selkie instead. Juno Clarke, hungry for redemption, asked what it was that had made it dead, and Miss Wallace looked a little sad and said it was the chlorine, that would have poisoned it long before the cold snap made the water freeze over. The chlorine would have filtered its way inside very fast, she told them, in a voice that tried to make it sound less painful than Freya was sure it was.

When the questions were over, 7C clustered around the body in the pool. The head was quite visible, from this angle: smooth, with black orb eyes, wide-set on a yowling face. Its nose was otter-like, a black pad of a snout that protruded enough to disrupt the human geometry of the skull. There were sprays of thick white whiskers on either side and the teeth below were small and sharp. The lower body was more obscured, but Freya saw a long torso, studded with dark nipples, curving into one great sinuous limb coiled beneath it. It was a dumb animal, and dead, but in that it was entirely beautiful.

It was nearly time to go back inside. 7C had had their fill of the mermaid’s dead hand, some of them were getting bored and were stamping their feet. Freya took her chance when Miss Wallace was distracted by Jason, who had found a pine cone and was proud of it: an ill trophy compared to what Freya had in mind. She ran her fingers over the back of the mermaid’s hand one last time, over its thick knuckles and into the folds of frost-crackled webbing. She found her target and she closed her fingers over it and pulled down hard.

It broke under the skin first. She was compelled to swivel it around the joint until the skin was torn all around, and even then it was difficult, it nearly sent her flying to do it. There wasn’t time to inspect her prize, just to thrust it down into the quiet black of her trouser pocket. She could feel it, small and cold and curled like a monkey nut. She squeezed her fist around it and the tiny spark of selfishness that had jumped inside her blazed, she was an inferno, she would collapse, if only something separated her from this fragment, this fossil of a perfect moment and a beautiful thing now dead.

As they trooped back up the stairway and into the honey warmth of the school, Joanna said it was funny, she had expected it to look more like a person. The others scoffed, but Miss Wallace heard her and said that it just went to show there was a world of difference between bipedal and human, and then Owen said Miss, how can it be a biped, it didn’t have any feet at all. Miss Wallace said that was a good point but in a voice that made it sound like she wished it was Owen there dead under the ice and trying to scratch his way out. She said that a mermaid physiologically speaking was an honorary biped, it was a biped in every way that mattered except the feet, and for homework she set them all the project of making up a word for things with two arms that humans and mermaids and gorillas could all be part of together, but not kangaroos or meerkats. Which seemed simple enough to Freya, as she caressed the gobbet of mermaid flesh in her pocket. Really, all it came down to was thumbs.