There are no secrets.
Or rather, there are few secrets - and fewer secrets still that will never be shared with those from whom, originally, they were intended to be kept.
It has been observed that the odds of a given secret getting out is inversely proportional to the importance of the secret in question.
Let us take, as an example, the pub which Severus Snape has habitually visited since shortly after leaving school. It is located on a nondescript street in a somewhat downtrodden section of Manchester. The pub - the Moon and Sixpence - is a Muggle one, of course, and while this would perhaps be viewed with some small suspicion by Snape's fellow Death Eaters (and discussed with a good deal of interest by those Order members who were unaware that Snape was a Half-Blood), it is not a terribly important secret. Wizards and Witches have always had their little Muggle-world peccadilloes and guilty pleasures. Even Lucius Malfoy, it is said, once - very briefly - kept a Muggle mistress.
Snape never shared any information about his pub of choice, because Snape rarely shared information of any kind. The location and nature of the pub itself, however, was utterly unimportant, and that was why the secret never got out.
So much for unimportant secrets.
A secret such as Severus Snape making an Unbreakable Vow that would result in the death of Albus Dumbledore is a far more important one, and so, of course, it would ultimately be shared with a great number of people, including, by a rather circuitous path, one Remus Lupin.
That Lupin - by a similarly circuitous path - happened to walk into the Moon and Sixpence for a drink on the third Sunday of Snape's tenure as headmaster of Hogwarts was purely coincidental.
Leaning against the bar, half pint of lager in hand, Remus gazed across the pub, realizing how unusual it was to have an opportunity to watch Severus without his knowledge. After the end of their fifth year in school, Severus seemed to have developed a sixth sense that alerted him when he was under observation; it was part of what made him such an exceptional spy.
Today, though, that sixth sense wasn't operating, or maybe Severus - who looked exhausted - was in no condition to heed its warnings. As far as Remus could tell, Severus hadn't even looked up when Remus walked in the door, and that was completely unlike him.
After taking a moment to deliberate whether or not it might be a good idea to simply leave the pub before Severus took notice of his presence, Remus shook his head. It would probably be safer for the Order - and for him personally - if he spent some time coming up with an actual plan before approaching Severus; Kingsley and Tonks had both reminded him just this week how important it was to be cautious about any scenario in which Severus was involved, and Remus understood their concerns only too well. However, he couldn't imagine being given a better opportunity for a private conversation, and surely that was important too.
In any case, was it really a question of caution, or was what he was feeling simply cowardice? In the end, he wasn't sure it mattered: regardless of what it was called, Remus was getting tired of being its poster child.
"Half again, please" said Remus to the barman, tipping his glass slightly. "And a half pint of whatever he's drinking."
The barman looked where Remus had indicated, then raised an eyebrow in surprise. "For Snape?" Remus nodded, and the barman shrugged. "What's life without risk, is what I always say. That'll be 70p for yours and 55p for the half of bitter."
Remus counted out the coins, then put the two glasses on a tin tray and walked across the room to the table at which Severus was sitting. Ordinarily, Remus would have just carried a glass in each hand, but things being what they were, he thought it might not be a bad idea to have one hand free to reach for his wand, just in case.
In the end, Remus's precautions proved unnecessary. He set the drinks tray down on the table before Severus even looked up.
"Mind if I join you?" Remus asked, sitting down across from Severus without waiting for an answer.
"Would it matter if I did?" Severus sounded as tired as he looked, almost as if he hadn't slept for a fortnight.
"Not really. Here," said Remus, pushing the glass of bitter across the table. "I've got you a top up."
"Is it poisoned?" Severus asked disinterestedly, as if he really couldn't be bothered if the answer to his half-serious question turned out to be 'yes.' He lifted the glass. "Cheers."
Remus raised his own glass in turn. "Cheers."
For a moment, neither man spoke as they busied themselves with the business of drinking, then Severus set his glass back on the table.
"I have to say I'm...surprised," Severus said finally. "I wasn't aware the Order had me under surveillance."
"We don't and you're not," Remus said. "At least as far as I know. I had a meeting with an informant in Cheetham Hill and happened to pass here afterwards while heading for an Apparition point."
Severus shook his head, a short, barking laugh pulled unwillingly from him. "Bloody typical. You 'just happened' to walk into my local." He lifted the glass and took another swallow, then set it back down on the table. "And after this? Maybe we can go down the chippy or visit the cinema together?"
The words conveyed amusement, but there was an all-too-familiar bite of steel beneath them, and Remus automatically touched the handle of his wand. It didn't do to underestimate Severus, regardless of what recent information had come to light.
"What do you want, Lupin?"
"We need to talk," Remus said.
"We have absolutely nothing to talk about," Severus snapped. "Or have you somehow forgotten that we are not on the same side in this damned war?"
Remus leaned forward, noting that Severus instantly took his own wand in hand. "I haven't forgotten," he said quietly. "However, I've recently been apprised about a Vow you took a little over a year ago."
For the briefest of moments, Severus was silent, his expression blank, but a reflexive tic in his cheek betrayed his discomfort.
"Well done," he said with a sneer. "You've discovered the rationale behind my most recent acts of self-preservation, because believe me, Lupin - I've had no thought in mind since making that Vow apart from saving my own skin."
"Yes," Remus said. "I noticed how concerned you were about your own safety when I joined you here at the table."
Severus scowled. "If you think I'm unable to defend myself against the likes of you, I invite you to step outside behind the pub."
"Enough with this idiotic posturing, Severus," said Remus. "Of course you're a better duelist than I am, at least under ordinary circumstances, but these circumstances are anything but ordinary. I know - as do Kingsley and Tonks, by the way - how the Vow related to...the headmaster's death."
"I killed him," Severus snarled. "I murdered Albus Dumbledore where he lay, and no Vow could have made me do that if I hadn't wanted to."
"Even if it meant sparing him more pain?"
Severus laughed bitterly. "You really are the most unbelievably naive...are you somehow unfamiliar with the requirements of the Killing Curse, Lupin? One has to want to commit murder."
"Yes, I passed my NEWTs, " said Remus quietly. "I also did a great deal of additional research in the Dark Arts after leaving school."
"Having nothing else to do with your days," Severus muttered.
"Fuck off, Severus," replied Remus. "But yes, I've had a great deal of time over the years to look into some rather arcane areas. Quite likely more time than you've had, and I've come up with some intriguing findings."
"If you're waiting for me to express interest in whatever inanity you have to share, you're going to be sitting here a very long time."
"Let's take Albus's hand, for example."
There was the briefest of pauses before Severus said flatly, "What of it? The result of an unknown curse, nothing more."
"Is that what he told you?" Remus asked. "Of course, that would make sense."
Making little effort to hide his action, despite being in a Muggle establishment, Severus tightened his grip on his wand. "What do you know?" he bit out between clenched teeth.
"The curse wasn't unknown, Severus. I recognized it almost immediately, and yes, before you ask, I discussed it with Albus, but he said you had everything in hand and implored me not to mention my discovery to anyone."
"And?" Severus said, practically vibrating with impatience and frustration. "What was it?"
Remus leaned closer. "Have you ever encountered, in your studies, anything about Horcruxes?"
Severus's eyes widened. "That complete and utter bastard," he muttered. "He knew. He knew all along and he let me waste so much fucking time."
"Trying to save his life," said Remus quietly.
Severus closed his eyes and raised his hand to squeeze the bridge of his nose. Without thinking about any possible consequences, Remus placed a hand on Severus's forearm, and surprisingly, Severus neither attempted to hex him, nor pulled his arm away.
"There's more, Severus."
Taking a single shuddering breath, Severus forcibly pulled himself together, before speaking. "What else, Remus?"
Without betraying a hint of the unexpectedly warm feeling that was brought on by the surprise of hearing Severus call him by his first name for the first time in decades, Remus said, "Riddle created more than one Horcrux."
"Apparently Albus told Harry there were seven, including the ring and the diary that was destroyed in the Chamber of Secrets."
"My sentiments exactly," said Remus.
"And Potter just shared all of this information with you, unprompted?"
Remus laughed and shook his head. "Of course not. Harry hasn't said a word to me about this."
"Then - ?"
"No, Severus. You have your sources and I have mine."
Severus smirked. "You've become quite the little secret agent man, haven't you?"
"Don't worry," said Remus consolingly. "You'll always be our favorite spy."
"You're about to get your wish," Remus said with a small smile. "I have to get back to London and update Tonks on this morning's meeting."
"Ah yes, and how is your beloved?" Severus asked, an unexpectedly mulish expression appearing on his face.
"She's not my...I'm not in love," Remus said. "I won't speak for Tonks, but...no, I'm not in love."
"And yet rumor has it that she carries your child."
"Well, rumor got it right then, didn't it? We're going to have a child," Remus said. "Or were you under the mistaken impression that babies only pop into existence in the cabbage patch when a Mum and a Dad love each other very much?"
"Lupin, I - "
Remus shook his head. "I'm not going to discuss this any further, Severus. Not now."
"Fine," Severus said sullenly, crossing his arms over his chest.
"Look," Remus said. "Maybe we can - "
"No, you're right," agreed Severus unexpectedly. "Now is not the time. What we must do now is arrange a future meeting, in case it's impossible to contact each other by the usual means."
"Next week, same place, same time?" said Remus, pleased - if surprised - by Severus's easy acquiescence. "I'll try to come up with some more information about what objects Riddle might have used for the remaining Horcruxes, unless...would you prefer to meet with Kingsley? Or Tonks?"
"Christ, no," Severus said. "I want you."
Remus's eyes widened and he smiled. "You do, do you?"
"As I believe I told you earlier," said Severus, his normally pale skin flushing a rather interesting shade of red. "Piss. Off."
Remus laughed, then got up from the table and buttoned his jacket. "Next Sunday it is then. See you then, Severus."