The Easter holidays were only two weeks long, but for Artemis, they felt a lot longer. She had spent the fortnight at her mother's tall, dark terraced house on Lovelace Crescent, and the silence had been even more marked than normal, thanks to the mandrake leaf Artemis was holding under her tongue. She couldn't tell if her mother had noticed that she wasn't talking, or if she just didn't care. Either way, Sara Hexley made no effort to engage her daughter in conversation.

The night the students finally arrived back at Hogwarts for the summer term was clear and bright.

"This is wonderful," Penny whispered to Artemis over dinner. "The full moon will be perfectly visible for us to make the potion. Talbott is going to meet us at sundown near Hagrid's hut."

Artemis gave her a tight-lipped smile and nodded her head, chewing and swallowing a tiny mouthful of cottage pie with extreme care so as not to swallow the mandrake leaf. She had gotten quite used to eating around the leaf, but with only hours to go until she would be using it to make the Animagus potion she was being extra cautious. If she swallowed it now, she'd have to start all over again.

At sundown, Penny and Artemis waited near Hagrid's hut for Talbott.

"He should be here any moment," Penny squinted at the path from the castle. "Do you see him?"

Artemis shook her head, and a large brown buzzard flew over the girls' heads. Suddenly, a voice came from behind them.

"I'm here," Artemis and Penny turned around to see Talbott Winger standing behind them. "I've got the dew."

"Talbott! It's lovely that you're here," Penny said. Artemis, still holding the mandrake leaf under her tongue, smiled at the boy. "How did you get here without us seeing you?"

Talbott did not answer Penny's question, but he lifted his gaze to the sky.

"The moon is coming out, we should start soon," he said. "It's quite clear here, but we should move a little further from the trees to get the most moonlight as possible,"

Talbott walked silently away from the edge of the forest, the girls following behind.

"When the moonlight is bright enough, Penny, you get out the vial, and Artemis will spit out the mandrake leaf."

They waited silently under the light of the full moon. Artemis could feel Penny becoming anxious, her eyes darting towards the trees that marked the start of the forbidden forest. She knew exactly what was on her friend's mind, and wished she could say something to make her feel less afraid. She used her forehead to gently nudge Penny's shoulder, and gave her a reassuring smile, which Penny returned.

At last, Talbott gave a swift nod of his head, and Penny pulled a small crystal phial from her leather potions belt.

"In here, Artemis," she said, holding the open phial under Artemis' chin. Artemis pulled the mandrake leaf out of her mouth and, feeling distinctly aware of the way her tongue moved in her mouth, placed the leaf into the phial. Penny held the phial up to the moonlight using her thumb and forefinger, rotating it gently. "I want it to take in as much moonlight as possible. You must be glad to not have that in your mouth any more!"

"Very," Artemis' voice sounded strange in her ears. Had she always sounded that way? "But I don't have an excuse not to answer any questions in Arithmancy now. How long does the phial need to be in the moonlight for?"

"I'm not sure, but I'd rather too long than not long enough."

"Whilst Penny is preparing the potion," Talbott said, so softly Artemis could barely hear him, "I need to teach you the incantation for the spell."

He took out his wand and placed the tip over the left side of his chest, where his heart sat beneath his rib cage.

"Amato Animo Animato Animagus!"

"Bless you," Artemis grinned. Talbott did not smile back. "Um, could you maybe repeat all that, but slower? Or write it down?"

Talbott did both.

"It's important you can cast this correctly," he said, his face grim. "From tomorrow morning onwards you will be casting this spell every single day at sunrise and sunset."

"How long for?"

"Until the next electrical storm."

"I think that should be enough moonlight, now. Artemis, I need one of your hairs next," Penny instructed. Artemis plucked a single strand of her untamable dark hair and handed it to Penny. Penny put the hair into the phial. "Talbott, did you collect the dew with the silver spoon I gave you?"

Talbott handed Penny a small pot and spoon, his eyes still fixed firmly on Artemis. His stare was inscrutable. Penny measured out the dew carefully, before producing an insect from a pouch on her belt, and placing both into the phial.

"And, finally, the Hawkshead moth," she looked up, closing the phial carefully and slipping it back into her belt. "We're done. We should head back. Before we get into trouble."

"You go," Talbott said. "I'll find my own way back to Ravenclaw tower."

"Thank you, Talbott," Artemis said as she and Penny turned to walk back to the castle. As they walked back up the winding path, she looked back in the direction of the forest to see whether Talbott was following them, but he had disappeared. Twenty feet or so in the air above them, the buzzard she had seen earlier soared over their heads. "Thank you, too, Penny."

"Oh, I don't mind at all, Artemis. I'm actually quite excited by it all."

Artemis chose not to mention to Penny the white flash of fur she had seen amongst the trees at the edge of the forest. It would only upset her, she thought, and, besides, it didn't really look that much like a wolf, anyway.

For the remainder of April, Artemis awoke early each morning to cast the Animagus incantation, and made sure that she was in her dormitory at sundown each evening to cast it again.

"How long do you need to keep reciting this gibberish for?" asked Tonks. She was lying on her back on her bed, holding a mirror in her hand, trying out different hair colours.

"Until the next electrical storm," Artemis replied, putting away her wand and sitting cross-legged on her own bed. Fergus came and rubbed his ginger cheeks against her upper arm, and she tickled him under his chin. "Hopefullly it won't be too long. I'm itching to get into the Restricted Section and find that Vault."

"About that," Tonks rolled onto her elbows, and looked at Artemis. "When you and Tulip go to the Vault, can I come? It's just that Penny and Rowan got to go with you last year, and I didn't mind or anything, but I kind of feel like I'm your only friend you haven't taken on a proper adventure yet."

"I'd love for you to come with us," Artemis said, absent-mindedly twirling Fergus' whiskers. "I mean, as well as being my friend you're the best in our year at Defence Against the Dark Arts. I could definitely do with your help."

"Cracking," Tonks grinned. "What do you make of the green hair?"

"It's a bit Slytherin, don't you think?"

"I hadn't thought of that," Tonks screwed up her face, and her hair turned back to her favourite shade of bubblegum pink. "You, me, and Tulip. The dream team."

Unfortunately, Tulip wasn't convinced that the three of them would make an adequate curse-breaking team.

"Merula is adamant about thwarting our plans, Artemis," she muttered to her as they found their seats in Transfiguration two days later. "I'm rubbish at duelling, and Tonks has her heart set on getting into the Vault if possible. We need a bodyguard."

"Easy," Artemis shrugged. "I know an excellent duellist."

That night at dinner, she sauntered over to the Gryffindor table, where Bill Weasley was eating his meal opposite his brother, Charlie, and Artemis' friend Ben Copper. Artemis plonked herself down into the empty seat next to Bill, who turned to her with an impish look on his face.

"Don't tell me, you've been hit with a dodgy colour-blindness spell," he said, and he pointed on finger in the direction of the Hufflepuff table. "You know, the yellow table is over there."

"Hilarious," Artemis stuck out her tongue at him. "You know, I've actually come over to proposition you."

"Ooh er," Charlie Weasley muttered into his cauliflower cheese, and Ben inhaled his pumpkin juice. Artemis gave them both a dangerous look that made Ben's cheeks grow two shades paler.

"And what exactly might this proposition involve?" Bill asked her, his eyebrows raised.

"I wanted to know if you'd be interested in another curse-breaking escapade," Artemis lowered her voice slightly. "I think the next Vault is in the Restricted Section of the library. I'm working on a plan to sneak in with Tonks and Tulip, but we really need a guard. Someone who can duel."

"So you want me for my brawn rather than my brains," Bill laughed. "Look, as much as I want to help you, I can't go breaking into Cursed Vaults right now."

"Why not?"

"Artemis, my O.W.L. exams are in less than two months. I really need to do well if I'm ever going to be a real Curse-Breaker," Bill shook his head. "Obviously, I do want to come along to the Vault with you, but it will just have to wait until the end of the exams in June."

"No," said Artemis. "I've waited long enough already."

"Then you'll have to get someone else to help you."

"Fine," Artemis sighed. "You know, you were a lot more fun before you became a prefect."

"And you were a lot less annoying when you couldn't speak." Bill laughed, and Artemis elbowed him firmly in the ribs.

"If it's brawn rather than brains you're after," said Charlie, "why don't you ask Barnaby? He's a really good duellist."

"You can't mean Barnaby Lee?" Artemis was incredulous, but Charlie merely nodded his head, nonplussed.

"But Barnaby is in Merula's gang," said Ben, with a shudder.

"He's actually a pretty decent bloke," Charlie shrugged. "He's just easily led astray."

"He sounds just your type, Artemis," Bill winked at her, and she elbowed him again.

"Do you think he'd even want to help me?"

"He might, if you ask him. From what I gather, you can be pretty persuasive," Charlie raised his eyebrows. "And he is quite drawn to people with power -"

"Slytherins," muttered Bill, rolling his eyes.

"- so if you show him how good you are at spellwork, he'll be more likely to want to help you," the other Weasley continued, ignoring his brother's interruption. "And I mean, really show him."

"What about when he finds someone better at duelling than me?"

"Artemis, we all know that's not going to happen any time soon. Besides, Merula's keeping Barnaby on her side with intimidation, not loyalty. If you make friends with him, actually make friends, he won't betray you."

Barnaby Lee spent most of his spare time in the Care of Magical Creatures paddocks. Artemis went there at the end of the day's lessons, and found him feeding lettuce to the Flobberworms.

"Barnaby," she called to him from outside the enclosure. "I want to talk to you."

"Merula told me not to talk to you."

"You don't have to do what she tells you," Artemis leant on the fence, watching as Barnaby shredded a lettuce leaf. "She's not the boss of you."

"She says she is."

"What? That's ridiculous," said Artemis. Barnaby said nothing in response. She sighed. "Barnaby, why are you even friends with Merula? She treats you horribly."

"It's better than not having any friends at all," Barnaby turned to face Artemis. "You wouldn't understand. It's easy for you to make friends, because you're so good at everything. I'm useless."

"I don't think you're useless," Artemis climbed up and over the fence, landing on her feet in the Flobberworm enclosure. "And neither does Charlie Weasley. He said I should talk to you, to see if you'd help me with something."

"What's that?"

"Something quite dangerous, actually. I need someone who is a powerful wizard, and he suggested you," Artemis stared at him, pointedly. "I want to get into a Cursed Vault. But Merula is trying to stop me, and I need someone who is able to take her down if needed."

"I can't," Barnaby Lee shook his head. "I'm supposed to be helping her, not getting in her way. And I'll never beat Merula in a duel, she's the most powerful witch in the school."

"She told you that herself, didn't she?" Artemis asked, and Barnaby nodded his head. "Well, if Merula is so powerful, how come I've duelled her twice and beat her both times?"

Barnaby looked confused. He put down the lettuce and walked over to her. He was easily head and shoulders taller than Artemis, but she looked up and stared at him unwaveringly, like she would a Hippogriff.

"You beat Merula twice?"

"If you doubt it, I'll duel you, too."

"I don't know," Barnaby looked Artemis up and down. "You're very small. I don't want to hurt you."

"I can deal with it," Artemis laughed. "Tell you what, do your worst. If you beat me I'll give up trying to convince you that Merula Snyde isn't worth your time."

"And if you beat me?"

"Then you'll have some thinking to do, won't you?" she smiled at him. "Come on. Let's see you duel."

Charlie was right, Barnaby was a very skilled duellist. But although his hexes were cast incredibly forcefully, Artemis found him easy to predict. Perhaps it was his body language, or the way he cast each spell so deliberately, but Artemis found that with each move he made she was one step ahead of him. It didn't take long for him to accept defeat.

"Fine, you win," Barnaby said. "You're too quick for me."

"Does that mean you'll think about helping me?"

"What's there to think about?" Barnaby frowned. "Merula's wrong. You're more powerful than she is. And much nicer, too. I'll help you."

"That's brilliant!" Artemis grinned. "You won't regret this, Barnaby. I promise."

As she left Barnaby to his flobberworms, she noticed a familiar looking buzzard flying from a tree to a stone halfway up the path back to the castle. As it landed on the stone, it vanished, and a boy in Ravenclaw robes stood in its place.

"Talbott!" Artemis walked faster to meet him. "What are you doing here?"

"What were you doing with Barnaby Lee?" Talbott asked, his eyes narrowed in suspicion.

"Trying to get him away from Merula. You didn't answer my question."

"I came to find you. How are you getting along with the Animagus spell?"

"Tediously. Been doing it every morning and evening without fail. I think it's starting to drive the other girls half mad."

"Well, you won't need to keep it up for much longer. There's a storm coming," Talbott must have seen the questioning look in Artemis' eyes, because he added, "Birds can sense these things."

"Right," she replied. "So what do I need to do?"

"When the storm comes, get Penny to give you the potion, and meet me on the Quidditch pitch. I'll help you with the transformation."

Artemis was awoken on the morning of the first of May by the collective weight of three fourteen-year-old girls simultaneously jumping on her bed.

"Happy birthday, Artemis!" Rowan, Penny, and Tonks chorused, thrusting presents under her nose.

"Hold on," Artemis reached to her nightstand, grabbed her wand, and pointed it to her heart. "Amato Animo Animato Animagus!"

"Now you've done that, will you open a present?" Rowan asked, and Artemis took the parcel she was handing to her. It felt suspiciously like a book.

At breakfast, a handful of owls arrived, one from her great-aunt and uncle, one from her mother, and one from Madam Rosmerta. Another owl, one that looked a little worse for wear, brought a box of fudge from a sender who hadn't revealed their identity.

Her friends visited the Hufflepuff table with hugs and gifts: some chocolate frogs from Ben, a Zonko's dungbomb from Tulip ("and Dennis!"), and a plate of rock cakes from Hagrid. Barnaby Lee didn't bring a gift, but gave her a quick smile and gruffly wished her a happy birthday.

"Looks like mum beat us to it," Bill said, as the Weasley brothers handed her a parcel. "I'd know her treacle fudge anywhere. Just be careful it doesn't glue your teeth together. I don't think you'll get away with another month of not talking."

Bill ruffled Artemis' hair and she pushed him away gently. As he did, Talbott Winger appeared at the Hufflepuff table.

"Talbott, how wonderful to see you," Penny beamed at him. "Have you come to join the celebration?"

"No," he said. He looked sceptically at the Gryffindor boys, and handed Artemis a folded scrap of parchment. "I just wanted to give you this."

Bill gave her a suspicious look as Talbott slipped silently away. Artemis opened the parchment. On it there was a rudimentary drawing of a cloud and bolt of lightning, along with a single word: Tonight.

"What in Merlin's name are you up to this time, Hexley?"

"Ask me no questions, Bill, and I'll tell you no lies."

After spending her birthday trying and failing to concentrate on her classes, Artemis heard the first rumble of thunder as she toyed with her dinner in the Great Hall. Looking up from her barely eaten beef stew at the enchanted ceiling, she saw that the ominous clouds had gathered.

"Penny," she said, pointing at the ceiling. "It's starting."

The two girls ran full pelt to their dormitory, where Penny collected the potion from the bottom drawer of her nightstand.

"Are you sure you want to do this?" she asked, handing Artemis the phial.

"It was your idea!"

"I know it was," Penny sighed. "But it all feels so real now!"

Talbott was already stood under the Quidditch stands when Artemis arrived at the pitch, soaking wet from the rain.

"You made it."

"I'm a fast runner."

Talbott walked wordlessly out from the stands onto the grass of the Quidditch pitch.

"When the lightning starts, the potion will turn red," he instructed once he was in the centre of the pitch. "You need to drink it, and then cast the incantation one last time."

"And hopefully not horrendously misfigure myself."

"Hopefully not."

"At least I can trust the potion, seeing as Penny's made it," she said. A question had niggling her from the day she had been introduced to Talbott. Now seemed as good a time as any to ask it. "Talbott, how did you and Penny become friends, anyway?"

"You don't understand why anyone as popular as Penny Haywood would want to be friends with someone like me?"

"I didn't say that," Artemis frowned. "You're just so secretive, that's all."

"Penny has secrets. You know what I mean."

"She told you about her cousin Scarlett?"

"She saw me feeding the Thestrals that pull the carriages from Hogsmeade station."

"I didn't realise anything pulled the carriages," Artemis said, before realisation dawned on her. Thestrals were winged horses that could only be seen by those who had witnessed a death. "Oh! That's why she was so spooked when we got into the carriages at the start of the year."

"Exactly, she'd never seen them before. So she asked me about them," Talbott looked at the sky. "We talked. I've never really talked to anyone before, but for whatever reason, I talked to her."

"Penny is very good at getting people to open up to her," said Artemis. She didn't want to pry, but found herself curious about Talbott's past. "Who... who did you see die? You don't have to answer if you don't want to."

"No, it's fine," Talbott pulled his gaze down from the sky and looked directly at Artemis. "My mum. She was killed by Death Eaters."

"I'm sorry," she said to Talbott, who said nothing. "She was an Animagus, too, wasn't she?"

"A swan. She was beautiful," Talbott said. "Her teaching me to become an Animagus saved my life. She made me transform and hide in a tree until the Death Eaters left. She couldn't do the same, because legally you have to register as an Animagus, so they knew about her."

"But you aren't registered."

"No. It's illegal, obviously, but it's safer this way."

"But You-Know-Who is dead. It's safe now."

"You really believe that?" Talbott asked. "A wizard that powerful, killed by a baby? No, he can't be dead. Not completely, anyway. And he still has plenty of followers out there, probably all waiting for him to return."

Artemis was silent. She was struck by the memory of the Boggart in Jacob's room. Overhead, there was another rumble from the sky, and a flash of light.

"It's time."

Artemis pulled out the potion. The mixture was changing colour, deepening to a bright blood red. She pulled out the stopper.

"Bottoms up," she said, raising the phial in a mock-toast, and she swallowed the scarlet mixture as another lightning flash streaked through the sky. She pulled out her wand and pressed the tip over her heart. "Amato Animo Animato Animagus!"

A strange sensation passed over her as the sky growled again. She felt a hot pain radiating through her, and a palpitation in her chest, as if she had two beating hearts instead of one. The lightning suddenly appeared bright, too bright for her to look at. She closed her eyes, but the bright light remained. A shadow of a four-legged creature burst through the light that blazed on the insides of her closed eyelids. When the light faded, she opened her eyes again.

"It's done," said Talbott. "What animal did you see? In the light?"

"A... a cat," Artemis stammered, her heart still beating faster than it ever beat before. "Does that mean..."

"Only one way to find out," he said. He didn't smile. "Think about what Professor McGonagall says in Transfiguration. Envision the transfiguration in your mind, then make yourself do it."

Artemis nodded, her front teeth pressed against her lower lip. She thought about the cat that she had seen leaping in the back of eyelids. She closed her eyes, and willed herself to transform.

When she opened them, the world was different. She was looking up at Talbott from maybe a foot off the ground, and everything in her vision had a greenish-yellow tint. She had never noticed so many different sounds and smells before, and even the air felt different as it brushed her cheeks. No, she thought, my whiskers. She thought about being Artemis again, and returned to her usual, girl-shaped body.

"It worked! It really worked," she gasped. "Thank you for helping me, Talbott."

"You're welcome," he replied, looking concerned. "Would you mind not telling anyone that I helped you? Or about my mum?"

"Of course not. I won't tell a soul, I promise," Artemis said, and she raised her eyebrows at Talbot. "Now, do you reckon a cat or a bird would get back to the castle quicker?"

For the first time since she had met him, Talbott actually smiled.

"I suppose there's only one way to find that out, too."

In his hut, Hagrid the gameskeeper looked out of his window at the storm. A buzzard was soaring through the thunderous sky. It looked like it was flying in the direction of the castle, and twenty feet below it, a very small and very fast tortoiseshell cat was bounding through the wet grass in its wake.