"What is this place again?" Colin asked, looking around at the mouldy walls, cracked mirrors and glumly dripping taps.

"Moaning Myrtle's bathroom," Maisie said, leaning over Mike's shoulder as he stirred the cauldron carefully.

"And who's Moaning Myrtle?"

Maisie and Mike exchanged glances. "Don't worry about her. Just keep your voice down."

"What do you mean, don't worry about her?" Colin whispered fiercely. "Is she a Boggart or something?"

"I'm not a Boggart!" a girl's voice shrieked. A transparent figure swooped out of one of the lavatory stalls and straight at Colin. He lurched backwards with a scream.

"Watch the cauldron!" Mike yelled at him.

Colin wrenched himself sideways, just missing knocking over Mike's cauldron, and landed on his back, staring up at what would have been a perfectly normal looking school-girl … if he hadn't been able to see straight through her. A ghost. This bathroom has its own ghost.

"That's right," the ghost said, drifting towards him as he scrambled backwards across the floor away from her. It was all very well for Maisie to dismiss ghosts with a wave of her hand, but many of them could hurt people, if they wanted. Peeves might limit himself to practical jokes on the nasty end of the spectrum, but having something large and sharp levitated up to drop on top of you wasn't much of a joke, and a ghost could probably manage to do it, if they were in the right sort of bad mood. "Don't think of my feelings. Nobody cared about my feelings when I was —"

"Myrtle, shut it!" Maisie snapped. "If you weren't so miserable all the time, people might not avoid you so much."

Myrtle soared up in the air with a wordless wail, and then turned towards Maisie. "You'd be miserable too if you'd been murdered in a bathroom."

"Maybe," Maisie said stolidly. "But I'd like to think I'd have more self-respect than hanging around clogging S-bends and literally scaring teenagers into wetting themselves."

"You're horrid!" Myrtle swooped towards Maisie. "Horrid! HORRID!"

She dived straight at Maisie, but Maisie stood fast, and Myrtle passed through her and vanished into the wall with another shriek.

Colin stared at Maisie. "Who — what —"

"The ghost of a girl who died in here," Maisie said. "Do get up, Colin. She's just a ghost."

He scrambled to a less undignified position. "She's a ghost who haunts a bathroom?"

"And why shouldn't I?" Myrtle demanded, appearing out of one of the toilets with a disgusting splash. "I suppose you think I don't have the right to, don't you? 'Oh, that Myrtle, she doesn't have the right to be here, she's not a real witch', that's what they said."

"You're obviously a real witch, Myrtle," Mike said, looking up from his cauldron. "Only a real witch could be a ghost, that's one of the rules."

Myrtle began to sob. "The only way I could ever prove I belonged here was to be murdered! Murdered!"

"Murdered?" Colin looked around nervously. "Who murdered you?"

"It was ages ago," Maisie said. "They're not hanging around now, Colin, I promise."

"How do you know?"

"Because when the prefects told us not to bother using this bathroom because it was haunted, I asked. She died in 1943."

"Oh." Colin stopped trying to peer under the doors of the stalls. "Then they're probably gone."

"They're all gone! No-one ever comes to talk to me, now! They only ever came when they wanted something!" Myrtle plunged back into the toilet and her next words echoed eerily up from somewhere near the S-bend. "You'll go too, and you'll never come back!"

"I think it's nearly done," Mike said, stirring carefully.

Colin crept towards Myrtle's toilet. Scary and see-through though she was, she sounded utterly miserable. "Myrtle, don't cry. I know it must be horrible for you, but there must be some things you like about being here?"

"Yes!" She erupted from the bowl again, drenching Colin in slimy water. "I like scaring people who are mean about me!"

He wiped his face on his sleeve. "But I haven't been mean, have I?"

She pouted translucently at him. "You don't like me."

"I was a bit startled."

"You thought I was a Boggart!"

"I asked if you were a Boggart, before I met you," Colin said. "I can see you're not, now, can't I?"

"You still don't like me. I can tell."

"I'm a bit scared of you," Colin admitted, and Myrtle smirked. "I mean, ghosts can be really powerful. They can do just about anything."

The smirk turned to a scowl. "I can't be alive again, can I?"

"Well, no, not that, but look at …" Peeves probably wasn't a good example to suggest to her. "Lots of ghosts. They help people. There's a ghost in the Gryffindor Tower who teaches students knitting, for example."

"I can't knit!"

"But there must be something you can do, right?"

"No!" Myrtle shrieked, soaring up towards the ceiling and hovering above him. "Everyone hated me when I was alive and everyone hates me now!"

"Colin, give it up," Maisie said. "She's been carrying on like this for sixty years, she's not going to stop now because you give her a quick pep talk. Besides, the potion's ready."

"That's right, go off and leave me," Myrtle spat. "Just like all the others."

"I'll come back," Colin promised her. "Do you like Gobstones? Or Exploding Snap?"

"I don't know," Myrtle said sulkily. "No-one ever wanted to play with me when I was alive, and no-one wants to play with me now I'm dead, either!"

"I'll bring some, then, and you can find out," Colin said, as Maisie grabbed his arm and towed him towards the door.

"How's she going to play Gobstones?" she asked as they all headed towards the staircase, Mike carrying the vial he'd poured the potion into. "She's a ghost."

"Peeves can move things around," Colin pointed out. "Maybe Myrtle can learn."

"He's a poltergeist, not a ghost," Mike said. "Honestly, Colin, do you never listen in class? Peeves was never alive. He's a sort of amortal being, not a ghost. Moaning Myrtle can't learn to be a poltergeist any more than Peeves can learn to be a normal ghost."

"Then I'll take board games, instead," Colin said stubbornly. "She can tell me what moves she wants to make, and I'll make them for her."

"It won't do any good," Mike warned. "Ghosts aren't like people. They can't really change. Myrtle must have been upset and sulking when she died, and she'll stay upset and sulking forever. Like the Fat Friar is generally cheerful, Nearly Headless Nick is friendly, and the Bloody Baron flies into a rage all the time."

"Well, I have to now, don't I? I promised."

"Hush!" Maisie hissed suddenly, pushing them back down the stairs. "Mrs Norris!"

The two boys hurried ahead of her back down to the landing and around the corner. "Is she coming down the stairs?" Mike whispered.

"I can't see her," Maisie murmured.

Colin cast a quick glance back over his shoulder as a draught stirred his hair, but there was no sign of Filch. A window open somewhere, maybe.

"She's coming, she's coming," Maisie said. "Back, quickly, get back."

Colin tried the nearest door. It was locked. "Mike, can you open this?"

"Hold the potion," Mike said, and Colin took it. "Alohomora!" Nothing happened. "Alohomora! It must be a magical lock."

Colin's knees trembled. Any minute now, Mrs Norris would stroll around the corner and fix them with her bulging, yellow eyes, and the next minute Filch would appear …

"Hello, puss," Professor Granger's voice said from the staircase. "I don't think you should be wandering around up here. Surely there must be some misbehaving students down in the dungeons for you to spot?" Mrs Norris gave a sudden, indignant yowl. "Oh, no you don't. No claws in teachers, that's the rule, or it should be. Now you just stop carrying on, and come with me."

The next moment the three students were treated to the incredible sight of Professor Granger, a struggling, meowing Mrs Norris clasped firmly in her arms, walking across the landing and down the stairs. Colin held his breath, but Professor Granger didn't even glance in their direction.

"Quick!" Maisie said. "Mrs Norris'll be off to fetch Filch the second Professor Granger lets her go!"

They hurried upwards to the fifth floor and the locked door. Mike held out the vial of the potion he'd brewed.

"Are you sure this is going to work?" Colin asked.

"I think so." Mike didn't sound nearly as certain as Colin would have liked. "It should keep working for an hour. Just take a small sip. We might need it again later, and I don't think I'll have the chance to steal more ingredients."

"You were brilliant to get them at all," Maisie said robustly.

Mike shook his head. "Not really. It was easy. I can see why Professor Granger's teaching assistant is just an assistant — he didn't even notice. He even sent me into the storeroom on my own."

"I wonder who he is," Colin said. "You didn't find out anything?"

"He's tall, I could tell from where his voice was. And he didn't sound young, or really old. Like, older than Professors Potter and Weasley but younger than the Headmistress. But apart from that …" Mike shrugged. "He was using an Invisibility Spell."

"You should have asked him to teach you," Maisie said. "That would be super useful, an Invisibility Spell."

"It's N.E.W.T level," Mike said. "I'd never get it right. Besides, I bet there's a policy against teaching students to turn themselves invisible." He grinned. "Filch would have a fit."

"And he never once mentioned his name?" Colin said.

"No. I just kept calling him 'sir'. I didn't really like to ask … he might not have been going to attack us, that day he disguised himself as Professor Granger, but he's not exactly friendly, either. Not like she is."

"I wonder what happened to him," Colin said. "It must have been really bad, to leave him so scarred-up he can't even show his face."

"He might have been born with it," Maisie said. "Professor Granger said 'disfigured' not 'scarred'."

Colin shook his head. "No, pretty much anything can be mended. The only thing they can't put right at St Mungo's is damage caused by Dark Magic. So I bet it was the War. Maybe he was one of the students who fought at the Battle of Hogwarts!" He grinned. "Which means we can find out who he is, because they're all listed. We just need to tick off all the male students who we know he isn't."

"Great," Maisie said, "but can we talk about it when we're not standing around in an off-limits corridor after-hours?"

Colin nodded hurriedly, thinking of Filch again. Mike took a tiny sip from the vial and gave it to Maisie, who drank and then gave it to Colin. He sipped as well. It didn't taste horrible, but it was certainly nothing he'd have drunk by choice.

"Right," Mike said. He took the vial back and tucked it in a pocket. Taking out his wand, he pointed it at the locked door. "Alohomora!"

The lock clicked open. Maisie put her finger to her lips, and opened it.

She went first, then Mike, leaving Colin to tiptoe in the rear. He pulled the door nearly closed behind him with a horrible feeling they'd forgotten something. Something about the Hungarian Hiccoughing Gas … something someone said …

The dust on the corridor floor showed their footsteps from last time, clearly marking how far they'd got before the gas. Despite Mike's potion, Colin tried to hold his breath as he reached the fatal part of the corridor. Don't hiccough … don't hiccough … don't hiccough … A strangled gasp from Mike showed that he was holding his breath as well, but ahead of him, Maisie was breathing normally. And not hiccoughing. Colin took a cautious sip of air, and then another when the first did nothing.

They were getting alarmingly close to the statue. Colin kept his gaze on it, straining to spot any sign of movement, but she seemed to be nothing more than an ordinary statue. Another few steps, and he was close enough to read the plaque at the base. Algernon Arbuthott, 1712 - 1832. He frowned. Algernon's an odd name for a woman.

He didn't have time to think about it, though, because ahead of him, Maisie was trying the handle of the door. It opened easily, and she stepped through. Mike, and then Colin, followed her.

He couldn't help giving a gasp of amazement as he took in the huge space before him, and then spun, horrified, expecting to see the flaming sword bearing down on him. When the statute didn't appear to have moved, he quickly closed the door on her.

"Merlin's moulting mantle," Maisie said, head tilted back to gaze up the ceiling, far overhead. "What do you think they use this for?"

"Indoor Quidditch practice?" Mike suggested, turning around to look at each of the walls in turn.

Colin winced at the thought of players colliding with the stone walls. "Maybe for practising spells that need a lot of space? Like, Summoning really big objects?"

"Elephants?"

Colin shrugged. "You never know." He stepped over to the nearest wall and ran his hand over the stone. It was cool and gritty, but seemed quite clean — a contrast to the floor, that was as thick with dust as the corridor outside. "Do you think the Quidditch Key is in here somewhere?"

"Where?" Mike turned slowly around again. "I mean, we'd see it, if it was, wouldn't we?"

It was true — the giant room was empty of furniture, of columns that might conceal something behind them, of shadowy corners or suspicious-looking cupboards.

"What's that?" Maisie said, pointing. Colin looked where she indicated, and saw a small lever on the wall. Before he could tell her what a completely mad idea it was, she'd crossed to it and yanked it firmly down.

He ducked, hands over his head protectively, but nothing happened.

"There's another one over here," Mike said.

"Wait!" Colin yelled at him. Mike stopped. "Just, wait a moment. Let's think. Anything could happen, if you pull that. A hole could open in the floor, or a Hippogriff could appear, or something."

"Move over to the wall, then," Maisie said. "Out of the way of holes or Hippogriffs. And you, Mike, pull your lever too."

Colin scrambled to the wall and pressed himself against it a bare second before Mike yanked down on his owe lever.

"Anything?" he said. "Colin, can you see anything?"

"No," Colin said, with a mixture of relief and disappointment. Nothing horrible had happened, which was good, but the Quidditch Key hadn't miraculously appeared, either. He edged away from the wall, looking around. "No, nothing."

"I bet it's like the nuclear launch keys," Maisie said. When the two boys stared at her in confusion, she sighed. "In the movies, there's two people who each have a key, right, and they have to turn them at exactly the same time, it's to stop any one person from making a mistake and causing a nuclear war." She released her lever, and it creaked back into its original position. "I bet we have to pull them at the same time, so you let go too, Mike."

Colin pressed himself back against the wall again.

"One, two —"

"Wait," Mike said. "Are we going on 'three' or on 'pull'? One-two-three or one-two-three-pull?"

"On three," Maisie said. "You ready?" Mike nodded. "Alright, one, two, three!"

The two of them yanked down on their levers at the same time. Somewhere overhead, stone rumbled, and Colin ducked again. When, after several moments, nothing fell on him, he straightened cautiously.

"Can you see what it is?" Maisie asked.

He peered around. "No. Nothing happened."

"Something happened, I heard it," she said. "Come here and hold the lever for me."

Colin edged over and took hold of the lever. It didn't explode or anything when Maisie let it go, so he held tight while she wandered out into the middle of the room.

"Anything, Maisie?" Mike asked.

"Nothing on the walls." She tilted her head back. "Ah, there! Up on the ceiling, do you see?"

Colin peered. "No."

"It's a little window. There's something in it — I think it's another lever."

"So we have to come back with brooms," Mike said.

Colin let go of his lever. "Come back?" he asked plaintively.

.

.

.

Author's notes: The differences between ghosts and poltergeists belong to JK Rowling, although from writing and interviews outside the books.

So, the Quest for the Quidditch key advances … and develops a possible sidestep.