The waves were werewolves today.

Artemis could see them appearing from the surface of the water before they came running towards her, the sound they made a menacing growl, the white sea foam their gnashing teeth as they chased at her heels, nipping at them as she ran to the shore. She mustn't let the teeth get her, that was the rule.

Luckily, she was fast. The were-waves were no match for her. Again and again, she ran in from the water, reaching the dry pebbles just in time. Each wave lapped at the shore behind her, each werewolf retreated back into the shadows of the sea from whence they came.

It was a good game, for a while, but it soon became repetitive. It would have been more fun if she had a friend to play with her, or her brother, but Jacob was not in the mood for playing today. He was sitting further up the beach, a book open on his lap in front of him. He had been reading the same book for longer than she had been running from the seafoam. Surely, he must be bored by now, she thought. Maybe she could convince him to play with her after all.

Jacob Hexley was almost ten years Artemis' senior, and in her opinion, there was no finer big brother in the world. He was cleverer than any adult she had ever met — except for maybe Daddy, but she wasn't sure she could count Daddy anymore — and a lot more fun. He alone knew how to fold paper napkins into flying dragons, he always snuck Artemis' cauliflower onto his plate so she wouldn't have to eat it, and he invented the best games.

The only downside to having him as a brother was that he spent more time at Hogwarts than he did at home. Artemis only ever got to see him at Christmas and Easter and, as was the case now, during the summer holidays. When she was really, really small, it hadn't been so bad. Her mum had been happy and good at making up games and telling bedtime stories. But, since Daddy died, the games and the stories had become fewer and further between. Nowadays, she spent most of her time just finding ways to entertain herself whilst she waited for Jacob to return home.

And now that he was home, he was too busy reading to pay her attention properly. That simply wouldn't do. She turned away from the sea and traipsed over the pebbles towards her brother, sitting quietly on the beach with an open notebook on his lap.

"What's that?" Artemis asked, leaning over Jacob's shoulder and squinting at the peculiar writing in the book.

Jacob chuckled. "None of your business, that's what it is."

But he couldn't have minded Artemis looking, because he did not close his book. Perhaps it could be a bit of her business, after all. Still, she couldn't read what was written. Not because she couldn't read, of course she could, she was a whole eight years and two months old now, but because the writing wasn't in English. Most of it wasn't even in the alphabet.

"What are all those funny letters?"

"They're not letters, they're runes," Jacob told her. Artemis frowned, and Jacob explained further. "It's a really old language. You know about different languages, right?"

Artemis rolled her eyes. "Obviously." She wasn't stupid. Still, she didn't know absolutely everything. "Where do they speak runes?"

"They don't, not anymore."

"What? So why are you learning it?"

"Because it's interesting."

That was a matter of opinion, thought Artemis. She screwed up her face.

"It's a waste of time learning a language that no one else speaks," she told Jacob. "You should do something else instead, like play with me in the sea."

"Of course, playing in the sea is never a waste of time," Jacob replied. The way he spoke made it sound a little like he was making fun of Artemis, but he ruffled her hair like he always did and turned to a fresh page in his notebook. With his quill, he wrote two words in his spidery handwriting: SLOSHY LIMES.

"What does—"

"Look."

Artemis did so, and with a wave of his wand, the letters on the page of Jacob's book wriggled around to form two new words: HELLO MISSY. Artemis giggled.

"Hello, Jacob," she replied. "Do another one."

"In a minute. Did you see what I did there? You didn't know what I'd written, because I'd jumbled all the letters around. But now you know that if ever you see the words 'sloshy limes' again, you'll know that it's someone saying hello to you. But no one else will know that, only you and me."

"So, it's like a secret code."

"Exactly. Same with the runes. If I know someone else who has learned about runes, I can use them as a code."

Now, Artemis understood why it might be interesting to learn about runes. If Jacob knew about them, and she learned about them, she could share his secret code.

"Teach me how to do runes," she told her brother, who laughed. "What?"

"It's a whole language, Missy. It takes years to learn properly. But okay." He picked up a pebble from the beach and pointed his wand at it. Tiny, funny letters appeared on the pebble. "In the olden days people wrote runes on stones. They didn't have room for lots of letters to make words, so each symbol is one word." He showed Artemis his pebble. "This rune means the sun. This one means water. This one means child. Here you go. You can keep it."

As he handed the pebble to Artemis, she frowned at the little symbols. "How do you know what symbol means what word if there aren't any letters?"

"You memorise them."

"Are there lots of different symbols?"

"As many as there are words," said Jacob, as if it were simple. It was not simple. There must have been hundreds or thousands or even zillions of words in the world. Artemis' mind boggled at the thought of memorising each and every one. Maybe runes were not for her, after all.

Still, she did like the idea of a secret code.

"Maybe it would be better to stick to the jumbled up letters," she said. "Can you do another one now?"

Jacob obliged. OWL ACQUIRED IN? he wrote.

But though Artemis stared at the letters and thought so hard her eyes and head started to ache, she could not unjumble the letters without her brother's help. Eventually, Jacob had to use his wand to help her.

LIQUORICE WAND? the letters now spelt out. Jacob reached into his pocket and pulled out a packet of sweets.

Artemis took one and bit into it. It was tough and chewy and more sour than it was sweet, and she wasn't entirely sure that she liked it. She definitely would have preferred to have an ice cream. But liquorice was Jacob's favourite, so it had to be good. She continued to gnaw on the liquorice wand anyway, digging her feet into the pebbles and looking out at the sea. The waves had calmed a little, as if the werewolves were resting, waiting for her to return so they could try to catch her again. The sun was high in the sky, and a salty-smelling breeze was cooling her bare legs, and her favourite person in the whole wide world was by her side.

"I wish it could be summer all the time."

"There isn't any point in wishing for things, Missy," Jacob replied. "Wishing never changes anything."

"I guess. But if it was summer all the time then you would always be here and we could come to the seaside and play and eat sweets every day." Though Jacob smiled, he did not look overly excited by the idea. Artemis sighed. "It's so boring without you and Ma is sad. I mean, she's always sad now, but she's definitely more sad when you're not here. Is she sad because of Daddy, do you think?"

"Yes," said Jacob. "So we have to look after her, don't we?"

It struck Artemis that this was a peculiar idea, that she should be the one looking after her mother. Surely, it should have been the other way around? But Jacob always knew best, and he was good at looking after everyone. Maybe she could be good at looking after people too, even if she was only small. Yes, she was certain that she could. She gave Jacob a definite nod of her head.

Her liquorice wand was not even half finished, but the taste of it had not grown on her. She was reminded yet again why she only ever ate the stuff when Jacob was around. Tired of working hard to chew the sweet, and even more tired of sitting still, she jumped to her feet and pointed the remnants of her liquorice wand at Jacob.

"On card!"

Jacob laughed, but he didn't get up. Artemis sighed again.

"Come on, Jacob. Play with me." She widened her eyes and tilted her head to one side. "Please?"

Remembering her manners must have done the trick, because finally, Jacob closed his book and stood up. He pointed his own liquorice wand back at her. "Titillandus!"

"What does that spell do?"

Jacob grinned. "It's the tickling charm," he told her, before running at her with his arms outstretched and fingers wriggling.

He was clever, but Artemis was quick. She leapt away from him and ran away, back towards the sea, squealing and giggling, the werewolves in the waves all but forgotten.