The plan was this: the following Wednesday evening, as Charlie finished his shift at the Three Broomsticks, Artemis would sneak out of the castle to meet him. From there, they would Apparate to Whitehall and enter the Ministry of Magic by the visitors' entrance they had used for the duration of their work experience placement.

"Are you sure you're okay about this?" Artemis asked, frowning at the tense look on Charlie's face. He gritted his teeth and nodded, but still seemed doubtful. "What's the matter?"

"Nothing," he told her, holding out his left arm. "I've just not done side-along Apparition before, and I'm not great at Apparating at the best of times. I just don't want either of us to get splinched, that's all."

"Don't worry about that," said Artemis, taking hold of Charlie's proffered arm. "Just concentrate on getting us to the right place, and try not to land us on top of any grannies while you're at it."

She grinned mischievously, and Charlie gave her a withering look before turning on the spot, gripping her arm with his fingers as he did so, as if he were afraid that he might leave her behind. But he did not leave her behind, for as he turned, Artemis felt the now all-too-familiar sensation of Apparition, and moments later, found herself standing beside him on the streetlight-lit pavement of a London street, beside a bright red telephone box.

"See?" she said, nudging his side with her elbow as she unlinked her arm. "You did it."

"Yeah, I guess I did," Charlie half-smiled. "And you're alright? One nose, two ears, ten fingers?"

"Of course. And look - no grannies harmed, either. Good job."

Charlie made a rude hand gesture as Artemis stuck her tongue out at him, and they both climbed into the phone box. Charlie used his left forefinger to dial five numbers, and Artemis picked up the receiver as a cool, clipped voice filled the telephone box.

"Welcome to the Ministry of Magic. Please state your name and business."

"My name is Artemis Hexley, this is Charlie Weasley. We're going to the Department of Mysteries."

There was a short pause before the voice spoke again, as emotionless and formal as before.

"Unfortunately, it is not possible to grant your request at this time," it said. Artemis turned to Charlie, whose red eyebrows were furrowed deeply. "Unauthorised persons are not permitted to enter the Department of Mysteries. If you wish to visit the Department of Mysteries, you must first submit a request to the Department. The Ministry of Magic apologises for any inconvenience. Have a nice evening."

"Wait," said Charlie quickly, as the doors of the phone box swung open. "We've actually already submitted a request, and it's been answered. We're here to go to... a meeting."

He shrugged at Artemis and crossed his fingers as they waited for the voice to answer him. Eventually, it did.

"Please state the name of the Department of Mysteries employee who authorised this request."

"Olivia Green," Artemis lied. "She's an Oracler, we're meeting her to talk about prophecies for our Divination homework."

"Thank you," said the voice. "Visitors, please take the badges and attach them to the front of your robes."

Charlie and Artemis exchanged relieved looks as the metal chute beneath the receiver began to rattle. Two badges landed at the bottom of it, and Charlie took them both, handing one out to Artemis, which read:

ARTEMIS HEXLEY, PROPHETIC MEETING ATTENDEE

She pinned the badge to her jacket as the phone box descended below the ground. Charlie exhaled loudly as he did the same.

"Can't believe that worked," he whispered. "Is Olivia Green even a real person?"

"Yeah, she was a friend of my brother."

"Visitor to the Ministry, you are required to submit to a search and present your wand for registration at the security desk, which is located at the far end of the Atrium," said the voice, before Artemis could explain further. The doors of the phone box opened to reveal the polished floors and walls of the atrium. "The Ministry of Magic wishes you a pleasant evening."

Not wanting to waste time or be caught, Artemis and Charlie hurried out into the atrium, which was far less crowded late in the evening than it was in the day. As always, the gleaming gold fountain in the centre caught Artemis' eye, and for a moment she had the sudden urge to go over to it, to wade into the pool at the bottom and find the small package her mother had given her back in August, the one she had discarded into the fountain's clear waters. But she shook her head and continued to follow Charlie across to the elevators. After all, she had far more important things to attend to tonight.

The Department of Mysteries was only one floor below the atrium, and so it was not long at all before she and Charlie found themselves in the dark corridor that led to the single black door, the one that had made Artemis feel so strange the first time she laid eyes on it, a sensation that had not yet faded.

"You alright?" asked Charlie, as he placed his hand on the door to open it.

"Yeah," replied Artemis. "There's just something about that door that makes me feel sort of weird, I guess."

"I get that," Charlie said. "Believe me, this place... Well, it's about to get a whole lot weirder, let me tell you." He raised his eyebrows and uttered one final word: "Ready?"

"Always."

With a nod of Artemis' head, Charlie opened the door, and gestured for her to go through it. Beyond the door was a single circular room, the walls of which were lined with a number of doors, all identical to the one they had just come through, which Charlie was now fiddling with.

"What are you doing?" Artemis asked him, as he pulled a school notebook from his satchel, ripped a blank page out of it, and cast a spell wordlessly to fix it to the door.

"Trust me," he said, with a shrug. "You'll want to know which is the way out in a minute."

Artemis wasn't entirely sure what Charlie meant, but she was willing to take his word for it. She turned away from him to look more closely at the room they were in. Including the door they had come through, there were twelve doors, all spaced evenly around the black walls, which were illuminated by blue-flamed candles. The floor was also black, and so well polished it looked almost as if there were a thin layer of water overlying it. Artemis shuddered; the darkness and illusion of standing in water reminded her of the Sunken Vault, and the loop of her own worst memories and nightmares she had seen whilst she was inside.

"Come on," she said, not wanting to be inside the room of doors any longer. "Let's work quickly. Which is the prophecy room?"

"I don't know."

"You don't know? But you said-"

"Look at them, they're identical. That's why I've had to mark this one," Charlie said, looking around at all the other doors. "We will just have to try all of them until we find the one we're looking for."

This was not something that Artemis had accounted for, but it didn't seem like they had any choice but to do what Charlie suggested, so she nodded.

"Which one do you want to try first?"

Charlie walked across to a door, stared at it for several moments, then shook his head and pointed to the one next to it.

"This one."

The door Charlie picked led into a room as dark as the one outside, with several orbs of various sizes floating in mid-air. As Artemis looked closer, she could see that they were not orbs at all, but planets.

"It's like we are in space," she mused, looking around herself and ducking as Saturn passed over her head.

"Yeah. This was where the Niffler started floating around," Charlie told her. "Let's try another one. Watch out for Uranus."

"Excuse me?"

Laughing, Charlie pointed to something behind Artemis, who jumped to the side, just as another planet floated by her.

"Thanks for the warning," she said, a grin playing on her own face. "Death by Uranus would be an awful way to go."

Still laughing, they made their way back out into the room outside, and Charlie marked the door the way he had the first. Before he closed it, he screwed his eyes shut. Artemis was about to ask him why, but the moment the door clicked into the doorframe, the world began to spin around her, the identical black doors rotating around the walls so fast that she couldn't keep track of them.

"Sorry," said Charlie, opening his eyes as the doors stopped spinning. "It made me feel really sick and dizzy last time."

Artemis nodded her head wordlessly. She felt dizzy too, and a little sick, but it wasn't because of the revolving doors. Or rather, it was, but not because of the spinning sensation. What made her feel lightheaded was the sense of déjà vu that she had since she arrived in the room of doors, and now had more than ever. The blue flames seemed to become blurry at their edges, and the dark shine of the walls and floors seemed to dull. It took her a few moments to realise that beside her, Charlie was calling her name.

"Artemis? Artie, what's wrong?"

Before she spoke, she blinked hard, allowing her vision to refocus.

"I'm sorry, I..." she shook her head. "I just realised that I've been here before."

"You have? When?"

"Lots of times, but also never. I've dreamed about it, and I saw it in my visions inside the Sunken Vault."

Charlie frowned. "Are you sure?"

"Certain," Artemis nodded, looking around herself again. "I thought it looked a bit familiar at first, but then, when the doors started to spin... It's these doors I've dreamt about."

"How can you dream about a place you've never been?"

"I dunno," said Artemis, shrugging her shoulders. "But maybe we'll find out whilst we are here." She pointed to the next door over. "Let's try this one."

She pushed the door, but it wouldn't open. She pushed harder, using the weight of her whole body, but it still wouldn't budge.

"It's locked. Alohamora!"

But the unlocking charm did nothing, even after three attempts at casting it. Artemis found herself growing impatient and frustrated, so when she pointed her wand at the door again, she did not attempt to unlock it at all.

"Bombarda!" she shouted, and though there was a loud bang as her spell hit the door, the door itself remained intact. "Bombarda maxima!"

Still nothing. Confused, Artemis stared at the door, and as she did, she thought that she could smell a slight aroma coming from it. She closed her eyes and took a deep breath in though her nose, and suddenly felt less frustrated and more calm.

It was as if she were no longer in the strange dark room deep underground at all, but on a beach, a sea breeze on her face, soft leather under her fingers, the taste of Firewhiskey on her lips, and the sound  of a bonfire crackling in her ears, the smell of toasted marshmallows wafting through the air. She felt free, and safe, and warm, and...

"I don't think we should open that door, Artemis."

The sound of Charlie's voice cut into her daydream, and she opened her eyes to find herself back in the room of doors. She turned around to see him standing several feet away from her; a slightly greater distance than she had thought. He was staring at the locked door with a peculiar mixture of emotions etched into his face, the most obvious one of which was fear. Reluctantly, Artemis nodded and stepped away, though her fingertips were itching and her heart aching to try again.

"No," she said, shaking her head and steeling herself. "No, you're probably right. You can choose next."

Charlie went to the door nearest him, and Artemis made her way across the room towards him, casting one last look over her shoulder at the locked door as she did. In the corner of her eye, she saw Charlie's gaze also drift back towards it.

"What do you think was in there?" she asked him, and he immediately stopped looking.

"I dunno," he replied, opening the next door. "But whatever it was, it... I think it was dangerous. Really dangerous."

"Because they keep it locked away?"

"Well, yeah. And because it smelt like it was about to blow up."

As they stepped into the next room, Artemis began to feel as uneasy as Charlie looked. The door Charlie had chosen led to a large rectangular chamber, with a tiered stone floor forming steps or benches like an ancient amphitheatre, descending down to a deep pit almost twenty feet below where Artemis and Charlie stood. In the centre, there was a raised stone daïs, on top of which stood an archway.

The structure was clearly unfathomably old, with deep cracks and crumbling edges to its stones, which looked as if they might fall down at any second. Yet somehow, the arch remained standing, a tattered black veil hanging from it and fluttering gently in the nonexistent breeze. Once again, Artemis got the feeling that the room, and the arch in particular, were distantly familiar, and once again, she was reminded of the visions that had plagued her inside the Sunken Vault.

"I don't like this," whispered Charlie. "I don't like this at all."

"You said that about the locked door, too," Artemis said, pushing away her niggling doubts to descend the steps. "I want to get a better look."

"Be careful."

"Obviously." Artemis rolled her eyes and continued traversing downwards, closer to the stone arch. The closer she got, the colder and stiller the air felt, but the veil continued to move as if someone were on the other side of it, tugging it with their fingers and lifting it with their breath. She could almost hear them whispering quietly to her. She strained to listen, breaking her concentration to ask Charlie, "Do you hear that?"

"Hear what?"

"That. The whispering."

"I don't hear anything."

"Come closer then," said Artemis, and somewhat hesitantly, Charlie inched his way down the stone stairs towards her. "Now can you hear it? I think it's coming from the other side of the veil."

Charlie frowned. "What veil?"

"The one inside the arch."

"What do you mean? The arch is empty."

But Charlie was wrong, or perhaps he just couldn't see what Artemis could see or hear what she could hear, because the veil was still swaying and the voices behind it still whispering. Maybe if she were to pull back the veil, just a little, she might....

"Don't touch that!"

A sharp, high-pitched voice rang out from far above and behind her, and Artemis immediately withdrew her hand. She turned around to see a cloaked witch standing in the doorway of the room, her face half obscured by her hood.

"Don't get any closer," said the witch. "In fact, come back. You aren't meant to be here, either of you."

The game was up. Artemis and Charlie shared looks of resignation before climbing the stone steps back towards the door, and the witch who stood in front of it. As they reached her, she lowered the hood of her cloak, and revealed her young looking face, brown curly hair, and thick-rimmed spectacles.

"Olivia Green," said Artemis.

"Artemis Hexley," said Olivia Green. "I was just sent a message telling me that you were here for our meeting about your Divination homework." She sighed, and seemed to become less bristly and more weary. "Do you want to tell me why you're really here?"

Artemis bit her lip as she thought of an excuse. "Um, well... It's about my dad."

"Your dad?"

"Yeah. He used to work here," she said, nodding her head definitely. "My mum's moved to America, and Jacob's in Azkaban, and so... I wanted to feel closer to him, so I came to see where he used to work."

Olivia Green's eyes flicked between Artemis and the stone arch.

"So," she murmured, "that's why you wanted to look at the arch."

"The arch?" Artemis looked back over her shoulder at the structure, the veil still whispering and waving within it. Her eyes widened with recognition. "The other side..." she whispered. "That's where they found him, isn't it?"

"Yes."

"Is it true? That if you go under the arch and through the veil, you die?"

Olivia Green fixed Artemis with a knowing look.

"Why do you think I told you not to touch it?" she asked. "You shouldn't have come here. There's a reason people aren't allowed in these rooms. The work we do, the things we study, they're dangerous."

"I know, and I'm sorry," said Artemis, trying her hardest to look ashamed. "I just needed to see where he'd been, that's all. I should have sent a proper request, but I thought it would be denied. I thought that you all probably wouldn't care, and would think that it's stupid, needing to know more about something like that."

"Yes, as people who dedicate their lives to studying the greatest mysteries known to mankind, we could never understand why someone might want to know more about something," Olivia Green muttered. She sighed again. "I can't believe I'm saying this, but come on. I'll show you the room where your dad did his research, and then you can go home."

"Really?"

"Yes, but you cannot tell anyone that I let you do this, okay?"

"No. Of course not. Thank you," Artemis said breathlessly. Olivia Green turned away, and she grinned at Charlie behind her back. Charlie raised his hand to scratch his arm, giving her a quick thumbs up as he did so.

"Follow me, then."

Olivia Green held the black door open for them, and as she stepped through it and out of the room, Artemis took one last look back at the stone archway.

"How long has it been there?" she asked Olivia. "The archway, I mean."

"A long time," was Olivia's answer. She shut the door behind her and the walls began to spin. "No one knows for certain. It's been here since the beginning, when the first Unspeakables discovered this place and used it to study."

"What, they just discovered that thing beneath the Ministry of Magic?"

"No. The Department of Mysteries predates the Ministry of Magic by a few centuries. The older areas of the Department were there before that. It's thought that they were the work of a witch or wizard from long ago."

"What, like Merlin?"

"Possibly even earlier. The Ministry built their headquarters above the research unit in order to better regulate and monitor the Unspeakables' activity," Olivia Green gave a wry chuckle. "Not that it ever worked, of course."

The walls had stopped spinning, and she walked straight across to one of the other identical black doors, apparently not at all disorientated. Artemis frowned as Olivia opened the door with ease.

"What's behind the locked door?" she asked. "The one that won't open?"

"Wow, you really have been making yourselves at home," Olivia muttered. "I'm afraid I can't tell you that."

"Because it's a really big secret?"

Olivia nodded. "I don't even know myself. It's never been unlocked, not since I got here."

"So what-"

"Did you want to see where your dad used to work or not?"

"Yeah, sorry," Artemis said quickly, and she and Charlie followed Olivia through the open door into yet another peculiar room.

The room was lighter than the others, illuminated by several low-hanging lamps that shone light onto the desks around the room. The desks surrounded a large tank in the centre, which was filled with a green liquid. Several items were floating in the liquid, and Artemis squinted to see what they were. Beside her, Charlie's nose was wrinkled in an expression of disgust.

"Are those..."

"Brains," said Olivia Green, leaning back on on of the desks, a disinterested look on her face. "Your father was studying matters of the mind and consciousness. He was specifically interested in the concept of Legilimency."

"Probably because Jacob and I are both Legilimenses," Artemis said before she could stop herself. Olivia raised her eyebrows.

"Possibly. He published a groundbreaking paper on the subject in the sixties. He went all the way over to America to study as part of his research."

Artemis nodded, and pretended to look closely at one of the brains whilst thinking of a way to get to the prophecies without Olivia realising that she was up to anything.

"Can we see where you work, too?" she asked, feigning mild curiosity. "You keep records of prophecies, right? That sounds really interesting, I'd love to see that."

Clearly, she had not been subtle enough in her request, because Olivia immediately stiffened and narrowed her green eyes at her in suspicion.

"Okay," she said slowly. "What's really going on here?"

Artemis widened her eyes and shrugged her shoulders, not sure what she could say to convince Olivia Green of her innocence. Apparently, saying nothing had the opposite effect, because Olivia stood up straight, and told her:

"If you two don't tell me now what you're really doing down here, I'll have no choice but to report you."

"No, you can't. No one can know we're here."

"Why not? Aside from the fact that your being here is breaking around seventeen laws, obviously."

"Because..." Artemis bit her lip and glanced at Charlie, who shrugged his shoulders. She was going to have to tell Olivia the truth. "Fine. We came here to find a prophecy."

"A prophecy? What prophecy?"

"One about the Cursed Vaults," said Artemis, and Olivia Green's eyes widened. "We think it's important - really important - and so we need to find out about it. The Aurors can't get it because there's someone passing information to R from inside their office, so we thought that we could come here and get it without anyone knowing. I'm not lying this time, I swear!"

Olivia stared at Artemis in silence for almost a full minute before telling her, "I believe you."

"You do?"

"Yes, your performance earlier was terrible, honestly," Olivia adjusted her glasses. "I think I know which prophecy you mean. Why do you think it's so important?"

"We aren't sure, but we think it's going to give us a clue about how to open them, and how Jacob and R are all connected with everything."

"So, you want to access the prophecy record?"

"We do. Can you get  it for us?"

Olivia Green sighed.

"No," she said simply.

"Oh," Artemis couldn't even be bothered to hide her disappointment. "Well, that's okay. I guess we've gotten you to break enough rules and laws for one evening."

"That's not why I can't get it for you," Olivia half-smirked. "Prophecy records can only be accessed by the person the prophecy is about."

"So, only Jacob can get the prophecy?"

"Precisely."

Artemis' heart sank. Their whole venture had been doomed from the beginning. She was never going to find out why R was so interested in Jacob after all.

But maybe she would, because Olivia Green tilted her head to one side and said, "Unless..."

"Unless?"

"Come with me. I have an idea."

Olivia Green strode out of the room without another word, leaving a mystified Charlie and Artemis to follow behind her. She led them back out into the room of doors, and as soon as the spinning stopped, strode straight across to the other side of the room and through one of them.

On the other side of the door was a room larger and colder than any of the previous ones, with a ceiling as high as that of the Great Hall at Hogwarts. The room was filled with toweringly high shelves, all holding what looked like small crystal balls, which glittered  in the blue candlelight.

"This is the Hall of Prophecy," Olivia informed them, not even turning back to look at them as she strode through the central aisle. "It's where I work, recording prophecies and storing them. The prophecy records are all in these orbs. If I'm correct, the prophecy you're after should be... Ah, here. Row 49, somewhere on that shelf."

She pointed to a shelf above Artemis' head and just out of her reach, and Artemis craned her neck as she struggled to see the prophecies.

"Here," said Charlie, also squinting as he pointed to one of them. "It's this one."

"How do you know?"

"Because they're labelled," he said. "And that one says 'Hexley' on it."

"That's what I thought," Olivia's voice called out from the central aisle. "If it doesn't specify Jacob Hexley, it might be that you can take it off the shelf after all."

It was worth a try, and so Artemis carefully placed one foot onto the bottom shelf, and climbed upwards until she could reach the prophecy. Now that she was high enough to see it properly, she could clearly read the label.

M.L.F., Date Unknown. The Vaults of Truth (Cursed Vaults) and ? Hexley.

Artemis reached out and placed her hand over the little orb, which was far warmer to the touch than she had anticipated, and glowed with a white wispy appearance within. Slowly, she raised her hand, and lifted the ball from its perch before climbing back down to the ground. In her palm, the white substance began to swirl, and a voice began to speak from within. The voice was a woman's, but the words were completely unintelligible.

"What is that? French?" Artemis asked Charlie, frowning. Charlie shrugged and nodded. "Do you understand it?"

"No. You?"

Artemis shook her head. "No, I don't speak French. But Penny does, she might be able to translate it if we take it back to her." She turned to Olivia Green and asked her, "I can take it with me, right?"

"Wrong," said Olivia Green.

"But it's got my name on it! It belongs to me!"

"No, it's about you," Olivia glared at her. "It belongs to - and in - the Department of Mysteries."

"But-"

"We record these prophecies religiously and in utmost secrecy. If you take that prophecy record, then the heads of the Department will know that I let you in here. I don't mind helping you, but I'm not going to risk my job for you."

There was a hardened look in Olivia's eyes that made Artemis relent. She sighed, and put one foot back in the lowest shelf to climb back up and replace the prophecy record.

"Here," said Charlie, holding out his hands. "Let me put it back for you."

Artemis handed him the orb and made her way back to the central aisle where Olivia was standing. Olivia led her and Charlie towards a side door that was opposite Row 53. This door opened to reveal another room, filled with dancing lights and clocks. Artemis tilted her head as she watched the lights sparkle.

"Time?"

"Time for you to leave," said Olivia, with a pointed look at Artemis.

She continued walking out of the sparkling room and across the room of spinning doors, right out into the corridor outside.

"Thanks again for helping us," Artemis said dutifully.

"Don't mention it. Really, not to anyone," Olivia told her. "It was good to meet you at last, Artemis."

With that, Olivia disappeared back into the Department of Mysteries, the door closing behind her with a gentle click.

"Well, there's never a dull moment with you around," said Charlie. "Come on. Let's get out of here."

They climbed into the elevator, and once they were one floor up, Charlie made his way back through the atrium at such a brisk pace that Artemis had to jog to keep up with him.

"Sorry," Charlie muttered, as soon as they reached the the city street above the Ministry. "I just wanted to get out of there as quickly as possible."

"Were you really that creeped out by it?"

"Not quite. I just didn't want to get caught with this."

Charlie grinned sheepishly and opened his satchel a fraction, revealing a small, glowing glass orb. Artemis' jaw dropped slightly, hardly able to believe it.

"Is that-"

"Yeah, it is."

A small but proud smile played on Charlie's face as he held out his arm, and Artemis giggled as she took it. There was a loud crack, and then the London street was as empty as if they had never been there at all.