"I can't believe Mr Filch confiscated your brother's notebook!" gasped Penny, after Artemis told her friends of the previous day's events over breakfast.

"He's an old git," Tonks scowled. "He took my entire bag of Zonko's products, too!"

"I just wish I could have seen Merula covered in bat bogeys," said Rowan, with a sigh.

"Actually, same here. Ugh, now I'm twice as annoyed!" Tonks said. She dropped her knife and fork emphatically onto the table. "Artemis, I think we need to take a stand against this unjust reappropriation of our rightful belongings. What do you say?"

"If that means going to Filch's office and demanding that he gives us our stuff back, then I completely agree."

"I was more thinking that we should break into Filch's office and take our stuff back," Tonks raised her purple eyebrows. "Somehow, I don't reckon Filch will be amenable to negotiations. A few loose fanged frisbees ought to buy us enough time to get in and have a good look around."

"But you just said all your Zonko's tricks were confiscated."

"I'm not the only person in this school who likes to shop in Zonko's, Artemis," Tonks said, and she got up from the table. "Let me go and speak to Jae Kim. He's brilliant at getting hold of contraband. You know, while I'm at it I might ask Charlie to have another go at hexing Merula, or at least get him to teach me how he did it."

She walked off in the direction of the Gryffindor table. Soon after, Rowan left to go to the library, leaving Artemis alone with Penny.

"Did you enjoy Hogsmeade, Penny?"

"Hmm? Oh, yes. It was lovely," Penny said. She smiled, but her eyes did not brighten as she did so.

Artemis tilted her head to one side as she watched Penny absentmindedly push her cereal around her bowl with a teaspoon.

They were now three weeks into October, but Penny was still just as withdrawn as she had been on the very first night of term. Artemis was the only one who seemed to notice, and she couldn't understand how it wasn't obvious to everyone that when it came to Penny, things just weren't quite right.

On the surface, Penny was acting like her normal, pleasant self, but there had been times when Artemis had caught her looking sad, or lost. Ever since she had found the Boggart in her plant pot, she flinched and closed her eyes every time she opened a cupboard, or a drawer, or her school bag, and she had now started to jump at loud noises.

In lessons, she seemed unable to concentrate, even in Potions, her favourite subject, and sometimes when she cast spells, her hands shook. In Transfiguration the week before they had learnt about Animagi, witches and wizards who could transform into animals at will, and Penny was one of only two students in the entire class who didn't applaud when Professor McGonagall transformed into a silver tabby cat in front of them.

Worse than that, she was hardly sleeping. By now, Artemis was used to the way the dormitory sounded at night: Rowan's snores, Fergus' gentle purr, the soft flapping wings of Tonks' bat, the ominous chewing noises that came from the Cruppy crate. Recently though, there was something different, something new, that made her feel uneasy. Although Penny was completely silent, it was as if Artemis could sense her presence, and if she tried hard enough, she could almost hear the sound of Penny's eyes blinking in the darkness and her tears rolling down her face to her pillow. She couldn't prove that Penny was lying awake at night, but each morning the subtle, bruise-like shadows under her friend's blue eyes were evidence enough that she was right.

"Penny, you know that if there's anything that's upsetting you, you can tell me, right?" Artemis asked her.

"Nothing's upsetting me. I'm fine," Penny replied. She did not look fine. Artemis frowned, and Penny looked away from her, avoiding eye contact. Penny smiled again, her eyes still blank, and changed the subject. "The Quidditch season starts again the weekend after next. Who do you think will win the Cup this year?"

Artemis sighed as her friend continued to act as if nothing was bothering her. But Artemis could see it, even if no one else could: something was definitely wrong with Penny.

Penny may well have been troubled, but at least one less thing was causing trouble for Artemis; Scully the Cruppy's training was now going from strength to strength, thanks to his new-found taste for rock cakes. Even Professor Kettleburn was impressed.

"Not bad for the runt of the litter!" he enthused, watching Scully turn in a tight circle on command. Artemis saw Merula glaring at her in the corner of her eye.

At the end of the lesson, while Professor Kettleburn was busy retrieving more Crup feed, and Bill Weasley's brother Charlie was showing Artemis, Rowan and Ben how he had taught his Cruppy to weave a set of poles, Merula decided to sabotage Scully. She took a bone off her own Cruppy, Morgana, and gave it to Artemis'. Morgana quickly turned on Scully, and it wasn't long before the two Cruppies began to fight over the bone.

"For Merlin's sake, Merula!" Artemis snapped, having realised what had happened.

"What? That bone belonged to Morgana! Your ratty little excuse of a Crup obviously stole it from her."

Merula's Cruppy was substantially bigger than Scully, and by this point had him pinned to the ground, snarling at him in a way that did not sound playful, yet Merula did not call her Crup away.

"Merula, you can't just allow your Cruppy to attack the others," said Charlie Weasley, more diplomatically than Artemis would have done, and he bent down to pull the two Crups apart. "Ow!"

"Are you alright?" Ben asked.

Charlie stood up, holding a squirming Scully in his right arm, his left hand held out in front of him. He tilted his hand slightly, staring at his palm, looking vaguely surprised.

Artemis' eyes widened as she realised: he had been bitten.

"Charlie, you're bleeding!"

"You should wash that cut out," Rowan said, leaning over Artemis' shoulder and peering at the two deep puncture wounds in the centre of Charlie's palm. "I don't think Crups have very clean teeth."

"Good idea. Aguamenti!" Artemis grabbed Charlie's wrist and drew her wand from her pocket. She pointed her wand at the bite mark, and a jet of water flowed from the tip. Charlie winced. "Sorry, Charlie."

"S'alright."

"It looks quite bad, you should probably get Madam Pomfrey to take a look at it," said Rowan.

Charlie nodded, and walked back to the castle with his Cruppy. Neither of the girls saw him for the rest of the day.

The next day was Halloween, and in the morning Charlie Weasley came over to the Hufflepuff table whilst Artemis and Rowan were eating breakfast with Tonks and Penny, his hand wrapped in a large bandage.

"Oh no," Artemis grimaced. "It wasn't Scully that bit you, was it?"

"Sadly not," Charlie shrugged. "Scully wouldn't have done nearly as much damage with his funny little mouth."

"Hey!"

Charlie started to laugh as he jumped out of the way of the toast crust that Artemis threw at him with all the strength she could muster.

"How long will your hand be bandaged for?" Rowan asked him.

"Next two weeks. Probably would have been longer if you two hadn't washed the wound out so quickly," he sighed. "Still, means I won't be playing Quidditch at the weekend. Can hardly catch the Snitch like this!"

"Oh, stop complaining, Weasley," Merula Snyde called over from her seat at the Slytherin table, a smirk playing on her face. "It could be a lot worse. It could have been a werewolf that bit you. Isn't that right, Haywood?"

Artemis felt Penny tremble in the seat next to her. She turned to face her friend, and saw that she was crying, her tears falling into her cup of tea. Artemis' heart sank.

"Come on, Penny, let's get out of here," she said, gently. She took Penny by the elbow, pulled her up out of her seat, and led her from the Great Hall to the Clock Tower courtyard.

They sat together next to the fountain, and Artemis put an arm around Penny's still shaking shoulders.

"Penny, talk to me. What's going on?"

"I c-can't tell you," Penny sobbed. "It's t-too horrid."

"You can tell me anything, Penny, however horrid," Artemis replied, but Penny shook her head. Artemis sighed. "Well, even if you can't tell me what's wrong, at least let me know what I can do to help you."

Penny sniffed.

"Well, there is something you could do."

"I'd do anything for you, Penny."

"I need to get hold of some Lethe River Water," said Penny, her face growing grim and determined. "Snape keeps some in his cupboard. But I can't get it by myself without him noticing. I need some kind of distraction."

"Well, you've come to the right person for that," Artemis grinned and nudged Penny's knee with her own. Penny didn't return her smile. "I do wish you'd tell me why, though."

But Penny refused to tell Artemis her secret.

The third year Hufflepuffs and Slytherins had Potions class later that morning, and Snape was getting them all to brew the Antidote to Common Poisons.

"Skip a few chapters ahead in the textbook," Penny whispered to Artemis, as they went to take their seats. "Page four hundred and ninety three. Antidote to Uncommon Poisons. If you make that instead, you'll distract Snape without having to do anything that's against the rules."

Artemis did as Penny suggested. The Antidote to Uncommon Poisons was a much trickier potion to brew, but she followed the instructions and found that she was capable of brewing the solution.

"Hexley, why is your potion so green?" asked Merula, peering at Artemis' cauldron and comparing it to her own. She stood up and leant over to look at Rowan's potion, which was more bluish in colour, like her own. She turned to Artemis and smirked at her. "Now you've done it," she hissed, and put her hand straight up into the air. "Professor Snape, I think Hexley's messed up again!"

Professor Snape swept across the classroom to witness Artemis' latest potioneering mishap.

"I thought the textbook said it was supposed to be bright green, Professor," Artemis feigned innocence, frowning at the book so as to avoid meeting Snape's eye. "Is that not right?"

"You've clearly looked at the wrong page number, Hexley. It's no wonder you are so useless at Arithmancy. What potion are you making?" Snape looked at her open textbook. "The Antidote to Uncommon Poisons. Miss Snyde, what potion should Hexley be making?"

"The Antidote to Common Poisons, Professor."

"Did I stutter, Miss Snyde, when I asked the class to make the Antidote to Common Poisons?"

"No, Professor," Merula's face looked like her birthday and Christmas had come at once. "You were very coherent."

"By next lesson, Hexley, I want you to write for me the instructions on how to correctly brew a Clearer Ear Potion," Snape said, and he examined her cauldron. "Thankfully, your potion-making skills have vastly improved in the past three years. Continue with your Antidote and bring a vial to me at the end of the lesson."

Snape swept away as Penny returned to her seat, one pocket of her robes bulging slightly.

"Thank you for helping me, Artemis," she said as they walked to the greenhouses for Herbology. "I really am ever so sorry about the extra homework. Don't worry, I know how to brew Clearer Ear Potion, so I'll write it all for you."

"I'd rather you just told me what the Lethe River Water is for," Artemis replied, but Penny shook her head and walked away.

Penny continued to act oddly during Herbology class. She seemed distracted, and Artemis caught her at one point staring at a valerian plant with a serious expression on her face. Artemis tried to talk to her again, but after the day's lessons ended, she slipped away without a word.

The Halloween Feast was that evening. Artemis had been looking forward to it all term, having missed most of the annual festivities in both of her first two years at Hogwarts. She took a seat next to Rowan and opposite Tonks, and watched as the ghosts performed a spectacular display of flying in formation, and listened to Professor Flitwick's Frog Choir.

Someone was missing, however.

"Where is Penny?" Artemis asked. "It's not like her to miss a social event."

"Library?" Tonks guessed. Rowan shook her head.

"I just came from there."

"Maybe she's at a get well soon party for Charlie Weasley's hand," said Tonks, and Artemis stood up and walked straight over to the Gryffindor table.

None of the Gryffindors had seen Penny all afternoon.

"I saw her at lunchtime," said Ben. "She was asking me about my secret room on the seventh floor. She wanted to know how to find it, and get inside."

Artemis' heart skipped a beat, and she turned on her heel and sprinted the whole way to the seventh floor, and paced in the corridor opposite the tapestry of the wizard with bloomers on his head teaching trolls to dance.

The door to the Room of Hidden Things appeared in the wall opposite the tapestry. Artemis entered the room and found Penny sitting cross-legged on the floor, a small cauldron bubbling in front of her.

"Hi, Penny," Artemis said, trying to sound casual. "What are you up to?"

"What does it look like I'm up to?" asked Penny. She did not look up from her cauldron.

"Potion-making," Artemis sat on the floor next to her. "I'm guessing this is what you wanted the Lethe River Water for."

Penny didn't answer. She was carefully decanting the potion into a vial, her wand gripped between her teeth. Artemis looked at the ingredients laid out on the floor next to the cauldron. There were a handful of valerian sprigs, which must have been why Penny had been loitering around the valerian plants in herbology, and a small pot full of white berries.

"Mistletoe berries," Artemis mused. "Hang on, this is was what we did for our first year Potions exam! That's a Forgetfulness Potion, isn't it?"

Penny closed the potion vial and removed her wand from her mouth. Slowly and silently she nodded her head. Tears were welling in her big blue eyes, which were fixed on her cauldron.

"Who is the potion for?"

"Me."

"Why?" Artemis received no answer to her question. "Penny, please. Just tell me what's going on. Why have you made yourself a Forgetfulness Potion?"

"To... to make me forget."

"Forget what, Penny?"

"Something that happened this summer," as Penny drew a deep shaky breath, Artemis held her own. She knew somehow that if she spoke now, Penny would go silent again. "When I was in Cornwall with my family. My grandparents own a little cottage there, and we've had a big family holiday every year since I was little. It's beautiful there. It's right on the cliff overlooking the sea, and if you walk down the cliff path, you get to the beach, and...

"And, well, one evening, me and my cousin Scarlett, we decided to go to a party on the beach with some boys we'd met earlier on in the week. You see, there was this lifeguard that we both thought was really good-looking, and we wanted to impress him," Penny blinked and let out a short, sharp laugh that sent a shiver down Artemis' spine. "We were just being silly, really. He was far too old and far too cool to be interested in either of us. I don't know why we even bothered going. I wish... I wish we hadn't."

Artemis stared unwaveringly at Penny, a sensation of dread creeping through her bones. The silence was deafening, but she didn't break it. Penny shuddered and closed her eyes tight.

"We stayed out on the beach until it was dark, and we were having such... such a good time, so much fun, that we didn't realise that we were way past our curfew. So, we walked back up the cliff path to the cottage and... well, we were walking, and we heard this noise, a rustling noise in a hedge. Scarlett said she heard something whimpering, like an injured animal. So she... she went over to see what it was, thinking that someone's dog was hurt, or something. And then... and then..."

Penny broke down in tears. Instinctively, Artemis shuffled closer to her, and wrapped an arm around her shoulder.

"And then?" she whispered.

Penny could hardly speak through her sobs. Eventually, she managed to find her voice again.

"It... it jumped out at her. But it wasn't a dog. It was a werewolf," for the first time, she looked directly at Artemis, who was staring at her in horror, her eyes wide and unblinking. "It attacked her, and I... I must have screamed, really screamed, because my mum Apparated there straight away and started casting all these spells. But it was too late. Scarlett was... she was already..."

As Penny started to cry again, Artemis wrapped her other arm around her, allowing her friend to dampen the shoulder of her robes with her tears.

"Oh, Penny. I'm so sorry," Artemis whispered into Penny's blonde hair. Penny lifted her head from Artemis' shoulder, and brought her hands to her face. The skin around her nailbeds was sore, as if she had been biting them. "Why didn't you say anything before?"

"I don't... I just couldn't. It was too hard. And I felt so... so guilty."

"But it wasn't your fault."

"It was my idea to go to that stupid party, and I was the one who wanted to stay later. If we hadn't gone, or if we'd left earlier, this never would have happened. And I'm a witch, I should have known it was a full moon, and I should have had my wand with me, and I should have been more careful."

"Penny, no. This wasn't anyone's fault but the werewolf that attacked you. You mustn't blame yourself."

"I just thought that if... maybe if I pretended that everything was normal, I'd start to feel normal again," Penny shook her head. Her whole body was trembling. "But it hasn't worked. I can't sleep, I can't eat, I can't concentrate. I just keep remembering what happened, and thinking how I could have stopped it, and..." her voice tailed off, and she picked up her vial of Forgetfulness Potion, holding it in her lap in both hands. "As long as I can remember, I'll never be normal again."

Artemis fought the urge to rip the potion out of Penny's hands.

"Penny," she whispered. "I know you think that making yourself forget everything will help, but I think this is too risky. What if you forget too much?"

"I'd rather that than carry on like this."

"I know you would, but Penny, what if you forget the wrong things? Like all your Potions, or Hogwarts, or your family? You might not be able to control what you forget.  Look at Ben, he still can't remember anything about what happened in the Cursed Corridor, and that was almost a whole year ago."

Penny said nothing, she just stared at the small vial of potion in her hand. Artemis changed tack.

"Penny, I know I can't understand what you're going through right now," she drew a deep breath. "But I have lost people, too. Jacob, and my dad. And I just know that if I had the choice to keep the bad memories from when Jacob went missing or when dad died, or to get rid of all of my memories of them entirely, I'd keep the memories. Good and bad."

After what felt like an age, Penny spoke.

"I don't know what to do."

"I can't tell you what to do, Penny," Artemis said, "but the way I see it, you can do one of two things. You can either take the risk and drink your potion, or you can come with me to see Professor Sprout. We can tell her everything, and she will help."

Artemis stood up and held out her hand. Penny stayed on the floor, chewing on her bottom lip and slowly turning the vial of potion in her sore fingertips. Artemis stayed perfectly still, scarcely able to breathe.

It might have been seconds, or minutes, or even an hour that passed, but eventually, Penny lowered the vial, reached out, and took the hand that Artemis held out to her.

Breathing a sigh of relief, Artemis helped her friend to her feet, and together, they walked hand in hand down the seven flights of stairs to find their Head of House.

Professor Sprout, having been dragged away from the Halloween Feast by Artemis, took the girls to the greenhouses, where they stood underneath her Wiggentree and told her what had happened. Sprout listened patiently to Penny's story.

"Dear child," she said, taking both of Penny's hands in her own and rubbing the backs of Penny's knuckles with her faintly green-tinged thumbs. "I am so very sorry that you experienced this. And I am sorry that you felt that you needed to suffer alone, when you have so many friends and myself who care about you and want to help you. But never mind that, you've told us now."

Penny sniffed and nodded her head. Artemis stared at her feet.

"Artemis," Professor Sprout turned to her, not letting go of Penny's hands. "I'm going to take Penny to the Hospital Wing. We need to have a chat with Madam Pomfrey. Please return to the dormitory, and don't repeat Penny's story to anyone. She will tell others when she feels ready."

"Actually," Penny said, in a quiet voice. "Would you mind telling Tonks and Rowan for me? They are my best friends, too. I don't want to keep secrets from them, but I... I just can't say it all out loud again."

"Of course, Penny."

"And Artemis?" for the first time in what seemed like forever, Penny's smile, though small and tentative, actually reached her eyes. "Thank you. For everything."