Hermione was deep in thought as she made her way to the entrance doors to meet the others. As soon as they were safely outside, Snape would be making his way to the Room of Requirement to hide. That'll fool Harry for a while, but not forever.

She couldn't tell anyone that he was there, but she hadn't made him any promises to prevent the others from working it out on their own. She and Minerva McGonagall were in a similar position, it seemed, although the Headmistress clearly had more information than Hermione had.

That's alright. She had every confidence that Harry and Ron would work it out for themselves. And then we can all put our minds to working out what sort of trouble he's in, that Minerva thinks he needs help with.

Even if he is just as nasty and disagreeable as ever.

She had to admit to a little bit of disappointment about that. In the years since his presumed death, she'd wondered from time to time if it had been an act, and had gradually allowed herself to believe that it had been. Snape's story was so sad, his actions so brave, his sacrifice so great, that it had seemed impossible the sneering, sarcastic teacher who had so often humiliated her could be the true face of Severus Snape.

Finding a patch of sunlight to wait for the others, Hermione grinned to herself. Well, that's me shown up as an idiot.

He had made a great many suggestions on her lesson plan, written all over it in fact, and they were admittedly useful, even if he'd explained them with his usual mockery. He'd taken her 'homework' with a raised eyebrow and muttered that he had too much to do to mark it, so she shouldn't hold her breath. He had also noted down the protective charms he used to keep his clothes from being regularly ruined by the inevitable accidents. They were slightly different to the ones Hermione already knew, and she was sure they'd be more effective. She was determined to be grateful to Snape for providing them, although the disdain with which he'd looked her up and down and sneered although it hardly seems worth the effort if you intend to wear that absurd get up made gratitude a bit difficult.

Well, so what? Snape is still Snape, that's all. It doesn't mean he didn't do all the things you know he did. It doesn't mean he doesn't deserve to be helped out with whatever problem he's got.

It just means he's going to be as snide and rude as possible to us while we do it.

"There you are!" Ginny sat down on the steps beside Hermione. "I meant to come down and give you a hand with your stock-take, but then I remembered that I was nearly out of handle polish and I had to nip off to the Owlery."

Hermione turned away for a moment to hide her smile. Professor Snape must have set something similar to the charms they used to keep Muggles away from the stadium for the Quidditch grand finals. He must have put quite a punch in it to affect someone as single-minded as Ginny. "It's alright," she said, when she could trust her voice. "It didn't take long. Professor Slughorn kept everything in pretty good order."

"Are you nervous?" Ginny asked. "I'd be nervous."

"I'm petrified," Hermione said.

Ginny leaned over and pinched her, and when Hermione jumped and yelped, the red-head grinned. "Nope, not petrified."

Hermione rubbed her arm. "Figuratively petrified. Everyone from Minerva to my house elf keeps telling me to dress the part, but I'm still not sure what the part actually is."

"Maybe it's just you, but more so." Ginny leaned back to look up at the sky. "I mean, that's what everyone else does, isn't it? Professor McGonagall is dignified and sharp-tongued, even when she's being friendly, except especially when she's teaching. Filius is exactly like you'd think he'd be, when you talk to him, from having been in his class."

And Professor Snape is exactly the same as a colleague as he was as a teacher. "Ginny, you're remarkably clever."

"I know," Ginny said smugly. "Don't tell Harry, though, he likes to show off."

Hermione elbowed her. "Harry knows better than to underestimate you. He'd better, or I'll have words."

"How about you?" Ginny's tone was overly casual. "Anyone special?"

Hermione snorted. "Yes, that's me, the sort of sweet young witch every wizard wants to sweep off her feet."

"I happen to personally know three young, handsome wizards who would happily sweep you off your feet if only you gave them the slightest encouragement."

"Who?" Hermione demanded.

"Oliver Wood —"

Hermione groaned. "Quidditch mad."

"Marcus Diggleby. He doesn't know a Seeker from a Bludger, if that helps."

"It does, but he's so damp."

"He just needs a good anti-perspiration charm, and a bright young witch like you could help him with that easily. No?" Ginny glanced her. "No. Alright, what about the Man of Mystery?"

Hermione frowned. "Who?"

"Nobody knows, that's why he's the Man of Mystery. But he's in potions, so you'd have plenty to talk about."

"Ginny, what on earth are you going on about?"

"Merlin's left buttock," Ginny said, laughing. "You bury yourself in the lab far too much. Someone wrote a letter to the Ministry last year with a recipe for a new healing salve. Surely you heard about it?"

"I knew there was an improvement," Hermione said. "Actually, I analysed it. Draco wanted an assessment on the potential for mass production, but without the patent, it wasn't profitable. It really was a very ingenious variation." She rubbed her arm, where the silvery scar had almost faded to invisibility due to that very same ingenious variation.

"Well, the letter was anonymous. They tried to trace the owl — I mean, someone who can do that sort of work, the Ministry wanted him on the payroll — but it turned out to be from one of those public owleries, and they never could find out where the letter came from." Ginny shrugged. "So they've been calling him the Man of Mystery."

"It could just as easily be the Woman of Mystery," Hermione pointed out.

"It could, but it doesn't sound as good."

"So you're suggesting I date either 'a', someone with whom I have absolutely nothing in common —"

"Who has very nice legs."

"— 'b' someone who I could, potentially, charm into a bit of sex appeal, or 'c', an anonymous potioneer who could be a woman or could be a hundred and seventeen for all you know."

"That's about the size of it," Ginny agreed cheerfully. "Or you could, you know, go out for a drink every now and again and meet people."

"They stare," Hermione said.

"Stare back," Ginny advised. "That's what I do. Look, there's Neville!"

She jumped to her feet and waved her arms over her head. Neville waved back, and quickened his pace towards them.

"It's good to see you, Ginny," Neville said, lifting her off the ground in a hug. Then a look of concern crossed his face, and he set her down quickly. "I didn't hurt you, did I? I heard you were spending more time here to see Poppy —"

"I'm fine, Neville," Ginny assured him.

"Luna said she'd meet us at the stones," Neville said. "So we're just waiting for —"

"Us," Ron said, jumping down the last few steps. "So let's go."

They started off towards Hagrid's hut, chattering and laughing in the warm morning sunlight. My silent mutual agreement, none of them broached the topic they were most interested in discussing: Neville talked about what it had been like to teach some of Professor Sprout's classes the previous year, Ginny explained her plans for her coaching, and Ron held forth on the topic of which of their D.A.D.A teachers had been the most hopeless.

"Penny for them." Hermione, lost in thought, realised Harry had dropped back from the others to walk with her. The Muggle expression — one that none of the others would understand — made her smile.

"I was just thinking about being back here, with all of you."

"You weren't, though," Harry said. "You were thinking about this secret you're keeping."

"How did you —?"

"You were biting your lip," Harry said. "Ron says you've got a right to keep it, and it's not harming you. Is he right?"

"Yes," Hermione said firmly. "And Harry, if I could tell you, I would — and I will tell you that I think you'll work it out for yourself, and I hope you do — but I gave my word."

"Good enough for me," he said easily, and slung an arm around her shoulders. "Although I've got one hand tied behind my back, haven't I, if you can't help me."

"I didn't say I wouldn't help you," Hermione said. "Just that I couldn't tell you."

He laughed. "And it's too much to hope that you'll lead us to the shortcuts, isn't it?"

She nodded. "I won't cheat."

Harry laughed again. "Of course you won't. Thank you for answering my question."

Hermione pulled away a little, frowning. "I didn't tell you anything."

"Oh, but you did." He let her go, and they followed the others side by side. "You, Hermione Granger, have no quibbles about cheating, or lying, or breaking the rules — when it's called for. Which means that whoever you made this promise to is someone you like and respect. You'd find a way around any promise you made to the Gilderoy Lockharts of this world, and you'd break one you made to someone like Umbridge without hesitation. You're determined to keep this one, which tells me the sort of person you've made it to."

The others had met up with Luna, and turned aside from the path. Harry and Hermione followed them.

"Tell me this, if you can," Harry said, just before they caught them up. "If your promise doesn't prevent you. This person — Ron thinks they're in trouble. Is he right?"

Hermione went carefully over the exact words she'd used. "Yes," she said after a moment, and thinking of the deep grooves that bracketed Snape's mouth, the tone of his skin, "And I think really bad trouble."

Harry nodded. "Alright, then. We'll just have to sort it."

The lot of them sat down on the grass in a loose half-circle. Hermione cast a quick and discreet Muffliato and Harry followed it up with a Disillusionment Charm powerful enough to make Hermione's ears pop.

"Lip-reading," he explained, tucking his wand away. "Right. Ron filled me in last night, but I think we need to go through what everyone knows, to start."

No-one questioned his right to take charge. "There have been strange doings in the dungeons," Luna said. "According to The Prophet, five parents complained to Minerva that their students had been frightened by a monster down there last year."

"What sort of monster?" Harry asked.

Luna shrugged. "Reports varied. So I'm thinking probably a Boggart, although that still leaves the question of why none of the teachers dealt with it."

"I asked Nearly Headless Nick about the new ghost in the dungeons," Neville contributed. "He said I had to talk to the Bloody Baron about it, but I couldn't find the Baron."

"But he said there is a new ghost?" Harry asked.

Neville screwed up his face, remembering. "Actually, no, not exactly. I asked about the new ghost, and he said 'the one you need to talk to is the Baron'."

Harry nodded to Ron, who leaned forward. "I talked to Professor Dumbledore and Headmaster Black, and they as good as told me that one of the teachers is in some sort of trouble, and Professor McGonagall can't ask for us to help." He shot a quick look at Hermione, and she fixed her gaze on her hands. "And they confirmed it's not a curse or a spell that stops her. She's not under any compulsion, and it's not something that would hurt the school."

"Which means she's made a promise." Harry shot Hermione a quick glance. "To someone she trusts, which fits with the idea it's a teacher." He pulled a folded parchment from his pocket. "I've made a list of who it might be. These are in alphabetical order. Weigh in with your opinions, everyone."

They all nodded, and he began. "Firenze."

"A centaur wouldn't be stupid enough to insist someone kept a promise when it hurt them," Luna said. "That's a very human thing to do, isn't it?"

"Professor Binns."

"He's dead!" Ron said.

"He might still need something," Luna pointed out. "Ghosts do pass on now and then, you know. Maybe he wants to."

Harry made a mark on the parchment. "Filch."

"Too nasty to have anything really bad happen to him," Ron said, and Hermione nodded agreement.

"Madam Hooch."

A general silence. "Right, Ginny. You're the best person to get close to her. Madam Hooch is your assignment. Professor Sprout."

"No way," Neville said. "I'd have noticed."

"If she was keeping it secret?" Hermione asked.

Neville nodded firmly. "I spend most of every day with her. She's the same as always. It's not Pomona, I'd stake my life on it."

"Alright," Harry said. "Professor Flitwick? Anyone?" There was another silence. "Flitwick's a candidate."

"I can keep an eye on him," Ron said. "I would be, anyway. Charms and D.A.D.A have a lot in common."

"Hagrid."

Hermione snorted. "Hagrid? All we need to do is ask, if it's Hagrid."

"What about Professor McGonagall herself?" Harry asked.

Ron shook his head. "I really had the feeling from what the pictures said that she's made the promise on to someone, know what I mean?"

Harry nodded. "Madam Pomfrey. Anyone?"

"I'll be spending time with her as well," Ginny offered. "I can feel her out, too."

"And Professor Sinistra?"

"I'll talk to her," Hermione offered. "And to Professor Vector, too. I always did well in her classes."

"That just leaves Professor Trelawney and Madam Pince."

"I'll talk to Professor Trelawney," Neville said, with a slightly long-suffering air.

"And I'll talk to Madam Pince," Hermione offered.

"That leaves me doing nothing," Harry said.

"Except breaking a twenty-year-old curse," Luna said.

Harry grinned. "Except that. I'll check out Binns, as well. Just in case. Alright. Let's go and see what Hagrid's keeping as a pet this year." He rose to his feet. "Last chance to get a bet down, everyone."

Hermione headed down the hill with Luna and Neville.

Harry and Ron lagged behind, and so Hermione didn't hear Harry muttering, "You catch that?'

"Yeah." Ron's voice was equally quiet. "It's not Sinistra, Vector, or Pince, or Hermione would have given then to one of us to check out."

Harry nodded. "That leaves Flitwick, Hooch, Pomfrey and Trelawney. And Binns."

"Five," Ron said. "What do you think, a week?"

Harry grinned at him. "At the most."