A/N: This fic was written in response to a prompt from Itchyfoot, who won the bidding at the TPP auction on LiveJournal. I offered to write a fic of up to 25,000 words for the high bidder. The prompt Itchyfoot provided was: "I'm envisioning an adventure/quest story with Snape as mentor to Hermione and maybe some other kids from Hogwarts. It would be nice if it extended to beyond the school years and even became friendship(s). All right I imagine any friendship with him would be angsty but that's the charm in knowing him. I'll let you and your muse decide on the level of romance." I don't think this came out entirely true to the prompt, but it's what the muse came up with, and hopefully itchy will like it regardless. It came in at around 20,300 words. Reviews, as always, are much appreciated.

Many thanks to Cat (quaffswinegaily), for the Britpick. Any errors are, of course, mine.

Severus stormed through the corridors, sending Gryffindors ducking behind whatever suits of armour they could find and forcing Hufflepuffs to dive out of his path with frightened shrieks. What could the Headmaster want with him that couldn't wait until after classes finished for the day? It wasn't as though the Dark Lord could have returned yet again – not after that mess five years ago. Unless the Golden Trio had somehow missed a Horcrux …

Well, no matter, Severus thought. As usual, the Headmaster called and Severus came running in response, even in the middles of a NEWT-level Potions lesson.

Reaching the gargoyle, Severus spat out the current password ("Sweet Tart") and swept through and up the stairs with barely a pause. He gave a perfunctory knock; upon hearing the Headmaster's call to enter, he swept into the room, robes billowing satisfactorily behind him. "What is so urgent, Albus, that you required me to dismiss my pupils forty-five minutes early? Their potions are ruined, as I'm sure you must know, so I don't want to hear complaints about the budget when I request replacement of the ingredients …" Severus trailed off as he realized that Albus looked unusually serious. "Well?" he demanded.

"Patience, Severus," Albus said gravely. "We must wait for everyone to arrive, as it is unlikely that I shall be able to repeat what I must tell you."

"What do you mean, 'everyone'?" Severus asked, narrowing his eyes suspiciously. "Who exactly are we waiting for?"

Just then, a knock sounded on the door, and Minerva let herself in without waiting for Albus to respond. "What's so urgent, Albus? My first years were just about to attempt their initial transfigurations when you called." She looked nearly as disgruntled as Severus felt.

"I must ask you to wait a few moments, Minerva. All shall be explained to your satisfaction shortly, I assure you," Albus said. A short silence ensued in which Minerva and Severus exchanged glances, each ascertaining that neither knew more than had yet been said. After a moment, Albus broke the silence, asking sombrely, "Would either of you care for a lemon drop while we wait?"

"Who are we waiting for?" Minerva asked, and Severus had a strong feeling of déjà vu. At least she appeared to be just as mystified by Albus's strange behaviour as he himself was. The Floo flared to life and the last three people Severus would ever have wished to see again tumbled out in quick succession. Granger came first, stepping rapidly aside and brushing stray ashes from her robes as she deftly avoided the fate of her two companions, who landed unceremoniously in a heap on the floor, a tangle of arms and legs that took a few minutes to sort out.

When they had finally righted themselves, Potter removed his glasses to clean the soot that was smeared across them as he asked, "What's the emergency, Professor Dumbledore? We came as soon as Hermione said you'd Flooed, of course, but we just couldn't think what could be so urgent. Things have been so quiet since we defeated Voldemort."

"I'm afraid a problem has arisen," Albus said seriously, "and I will need assistance from all of you to solve it. I appreciate that you have responded so quickly to my summons, but there are two more persons we must await before I explain everything."

Potter looked about to protest, but Weasley beat him to it. "Can't you just tell us now, Professor? We can fill in the others when they arrive …"

But Albus just shook his head sadly. "No, I'm afraid that won't do, Mr Weasley," he said firmly. "I shall likely only have the strength to say it once, so we must wait for everyone."

Severus frowned as Granger, sounding alarmed, asked, "Are you ill, Headmaster? Should we send for Madam Pomfrey?"

"Thank you, Miss Granger, but she is already on her way."

Granger subsided and silence fell again. Severus examined the people in the room, trying to discern what sort of problem would lead Albus to call this particular group of people together. Potter and Weasley were both Aurors – they had entered training immediately after Hogwarts. Once that was complete, they had immediately joined the Dark Wizard Apprehension and Retention Fellowship, a subdivision of the Department of Magical Law Enforcement that spent all its time hunting rogue Death Eaters who had possibly escaped punishment after the war. Their jobs were made somewhat more difficult by the fact that, upon Voldemort's final demise, the Dark Mark that would have made initial identification easy had simply vanished from everyone who had had the misfortune or bad judgment to have one.

So perhaps this had something to do with rogue Death Eaters, Severus thought sourly. Would they never be finished rounding them up? But though that might also explain his own presence, it didn't clarify in the least why the two women were here. Minerva, for all her work with the Order of the Phoenix and her efforts in the final battle, would have nothing unique to contribute to the hunt for Death Eaters. And Granger – technically, Unspeakable Granger – had joined the Department of Mysteries rather than the Aurory after the war, so she was unlikely to be called in on a simple DWARF mission. Unfortunately, Severus had no idea what Unspeakable Granger actually did in the Department of Mysteries, so he was fated to remain in the dark until the other people arrived. He shied away from considering what it could mean that Poppy was expected to join their number. Though Albus often elicited a distinct urge for Severus to hex him, Severus knew that the old man was as close to a father figure as he would ever have. He wouldn't think about the possibility that the old man was sick …

Eventually, Severus's deliberate not-thinking about what could be wrong with Albus was interrupted as Poppy came bustling in. "I'm so sorry to keep you waiting! Martin Anderson accidentally transfigured Mary Jameson into a toad – they were practicing for Transfiguration lessons, they said – and I felt I ought to reverse that right away."

Albus assured Poppy that he wouldn't have expected otherwise. Moments later, Horace Slughorn arrived, grumbling about how tiring it was for someone of his advanced years to navigate all those stairs. Severus pondered what all of this could mean even as Albus cleared his throat and began to speak. "I know you're all wondering why I've called you here. It is my grave duty to tell you that I need your assistance most urgently – all of you – because of an incident that seems to have occurred in Hogsmeade mere hours ago."

"In Hogsmeade?" Weasley interjected, as a general murmur of bewilderment seemed to echo amongst the gathering. Albus generally was not known to leave Hogwarts in the middle of a school day.

Albus said, "Please, save your questions until I have finished, if you will. Now, as I was saying, I was on my way out of Hogsmeade, having just left Honeydukes, when I began to feel the effects of what I can only surmise must have been some sort of Dark Magic. Of course, I looked around immediately to see if I could identify anyone as the source of the curse or jinx or whatever it was, but perhaps it was something slow-acting. I saw nothing out of the ordinary, unfortunately, and so cannot give you more information about who was responsible or even exactly when it hit me. That being the case, I deemed it best that I come immediately to Hogwarts and assemble the people who are best qualified to determine what happened and to reverse the effects."

He fell silent; for a moment no one spoke. Then, predictably, Granger asked a question. "If I may, sir, what precisely are the symptoms you are experiencing?"

Albus sighed. "That, my dear, is rather more difficult to explain than you might expect. It's a feeling that something is missing – some integral part of myself, or perhaps of my magic, is just gone. Either way, I have felt myself weakening since the event occurred. In addition, my usual optimism has deserted me and I can only assume that, if a countercurse is not soon found, I shall simply fade away."

Potter jumped in. "So, you wish us to determine who has cursed you?"

"I had hoped you and Mr Weasley, along with Professor Snape and Unspeakable Granger, might undertake the task of finding the wizard or wizards responsible and determining the remedy for this situation." The Golden Trio was nodding emphatically. Severus restrained the urge to groan. Would he never be free of them?

"What of the rest of us?" Minerva asked sharply. Severus recognized that her less-than-pleasant tone was symptomatic of her worry, and Albus did, too, apparently.

"Well, Minerva, I had hoped that you would manage my duties as Headmaster. Horace, someone will need to teach Potions while Severus is occupied with this task; may I count on you?" Slughorn nodded, looking grave. "And Poppy, dare I hope you'll be able to assist me with managing any symptoms that might appear while a cure is sought?"

"Of course, Headmaster," Poppy said. "Severus, if I might consult with you briefly before you begin your investigations?"

Severus wasn't sure what help that would be, as he had no idea what sort of Dark Curse might have had such effects, but he agreed anyway. "Very well. Albus, perhaps Poppy and I should settle you in the Hospital wing now? Miss Granger, Mr Potter, Mr Weasley, if you will remain here, I shall return shortly and we can determine our best initial avenue of investigation." He stood and took Albus's arm.

Weasley interrupted. "Harry and I should go down to Hogsmeade and try to find witnesses."

"No, Mr Weasley, you should do no such thing until we have had an opportunity to confer about this," Severus snapped. "Rushing headlong into the breach will do us no good and might set us back if you muck things up as you usually do." Honestly, if it were anyone but Albus in this predicament, he would leave them to their own devices. But it was Albus, so he would find a way to work with them, one way or another.

"Hey!" Potter cried. "That's not fair, Snape! We've been very successful –"

Severus was about to snap back again when a surprising voice took his side. "Professor Snape is right, Harry. We have no idea what we're dealing with, and we should try to determine what we can before you go haring off to question people." Weasley started to protest again, but Granger glared at him. "I'm not kidding, Ron, you and Harry should stay put until Professor Snape gets back and we have a chance to discuss strategy. You wouldn't start a chess game without at least a start of a plan, would you?"

Severus was surprised and reluctantly impressed with how quickly Weasley and Potter both subsided. They both looked sulky, though, so Severus said, "While I'm gone, perhaps you would begin to formulate a plan of some sort, Miss Granger?"

Granger nodded, and Severus assisted the Headmaster as they left the office with Poppy.