Sirius paused for a moment at the top of the dungeon staircase, not at all eager to plunge into the semi-darkness of Snape's domain. As unnecessary as it was, with Hogwarts nearly empty for the holidays, he looked around cautiously, his fingers twitching involuntarily toward the wand in his pocket.

Everything was silent. No concealed enemies stirred in the shadows of the dimly lit hall.

He took a steadying breath and stepped into the stairwell. He shivered, and told himself it was because the temperature dropped like a rock as you entered the dungeons, or because the damp stone walls and lack of light reminded him of his Azkaban cell. Not because he feared whatever it was Snape was going to do to him. Definitely not.

It had been a fortnight since Sirius had come crashing back through the Veil in the Department of Mysteries, and found the world altered. Albus Dumbledore dead, his body charred and blackened beyond recognition by a Dark curse. The Ministry in disarray, too slow in accepting the truth of Voldemort's return to keep from crumbling like a tower of cards in a game of Exploding Snap. Remus, only holding together by a frayed thread, but trying to stand steady for those who clung to him. Harry -- his godson Harry, with James's face and Lily's eyes -- changing with each passing day since his sixteenth birthday, and the letter from Lily, sent by time-delay so many years ago, that explained why. The mounting death toll. The horcruxes. And Snape....

He had known, from the moment the inside of his head had finally stopped spinning long enough for him to take in what he was being told, that Snape would not wait long before calling in the life debt Sirius now owed him. In all likelihood, he had waited this long only because he suspected what the wait was doing to Sirius. And now Snape had tired of waiting, and Sirius would at last know what the price of his return to this side of mortality was going to be.

He tried to square his shoulders and stand taller as he reached Snape's door, but the truth was that he didn't feel at all Gryffindor-like, and, besides, knew that marching in with a sneer on his face and a devil-may-care glint in his eyes would only make facing whatever it was Snape demanded from him that much harder. Snape did love to wipe that sort of look off people's faces. Still, he hated to go in looking like he felt. Like a worm cowering before a sharp hook.

It did no good to stand there staring at Snape's closed door, so he raised his hand and knocked, and when the lock clicked he pushed the door open and walked in. He tried to keep back a wince as the door shut behind him, the lock clicking into place again.

He had never been in Snape's private rooms. Didn't know anyone who ever had been and lived to tell of it, actually. Except maybe Dumbledore. He thought it was a particularly bad sign that Snape hadn't called him into his office, or, as Sirius had supposed he would, humiliate him in a very public way. Whatever Snape wanted from him, the fact that he would reveal it only in this most private of places, far removed from the scrutiny of others, seemed to bode ill.

It was dark. Coming in from the corridor outside, which had been lit only by low-burning torches, it still took time for Sirius's eyes to adjust to the darkness in the cavernous room. The main source of light was a row of candle stubs across the length of the massive fireplace mantle. Their flickering light could not hope to illuminate the room. On the opposite side there was a long, low table, and it was the fire underneath a dozen small cauldrons that provided the only other light.

Sirius looked around warily. He didn't see Snape, but knew that Snape was there, watching him from the impenetrable shadows. It made the hair stand up on the back of his neck.

Like a ghost, Snape's black-clad form materialized behind the potions table.

They stared at each other in silence.

"Snape."

"Black."

There was something comforting in exchanging this customary, barely civil greeting. Still, he tried to keep the customary scowl off his face.

"Light still hurts your eyes?"

"A bit."

It did no good to try to search Snape's face for clues to his intentions. Snape's expression was as blank as a block of marble.

"Well, you called, and here I am." It sounded flippant, but it was too late now. It always happened just like this, with all good intentions flying out the window within a few moments spent in Snape's company. "Do I get to sit down, or will standing do for you?"

"It will do." Snape's voice didn't rise, and his expression didn't change.

Sirius swallowed nervously. It was, perhaps, fortunate that his mouth had gone bone dry, preventing him from saying any other foolish things.

With carefully measured steps, Snape came around the table, stopping in front of it, still a good distance from Sirius. There was a certain tension in the way he held himself, that suggested he was perhaps ready to go for his wand at a second's notice.

That didn't mean much, of course. They were all twitchy these days.

"I'm calling in the debt you owe me."

Sirius stayed silent. It was more from necessity than anything else, because it was hard enough to breathe around the lump in his throat, let alone attempt to speak.

"I have considered what you might be useful for, and I settled on a number of tasks that I wish to get off my hands."

Sirius almost opened his mouth to protest that it was unfair, it was breaking the rules to demand more than one thing of him, but it occurred to him that Snape had probably thought it out and had an argument ready, listing all the reasons and ways Sirius owed him. He saved himself the trouble by keeping his mouth shut and his teeth gritted.

Indeed, Snape had apparently been expecting him to say something, for he had paused and was eyeing him mistrustfully. Expecting him to struggle against the bonds of his debt to the bitter end. A few moments passed before he went on, as if only then deciding that no outburst was forthcoming. "I have a supply problem. Gringotts has revoked access to my vault. No doubt --" Snape's lip curled into an ugly sneer as he said this, "-- the Ministry will eventually get around to correcting the mistake. Nonetheless, I require certain items if I am to continue to produce potions other than those required by the school curriculum and the infirmary, and paid for out of school funds."

Wolfsbane came instantly and painfully to Sirius's mind, even before the small sense of relief that the first task Snape seemed to be handing him involved nothing more than a trip to the Apothecary. And if Snape's vault was never returned to him and the arrangement stretched endlessly, well, he supposed the Black vault could stand it.

As if knowing that he had been understood, Snape didn't explain further, but took out of an inner pocket of his robes a roll of parchment tied with a black ribbon. "A list."

The parchment was held out to him, making it necessary, for the first time, to approach Snape. Reluctantly, he did so, and took it. He pocketed it without unrolling it to see what was on it.

"You may know that I was able to retrieve a number of books from Malfoy Manor, before it was abandoned by the opposition --"

The opposition. Sirius almost laughed.

"-- and seized by the Ministry. There are a number of additional items I wished to take with me, but was unable to do so due to circumstances beyond my control."

Such as having been blasted by a curse that left him nearly blind, Sirius supposed. Most people would have dropped any thought of carrying out souvenirs in favor of getting out alive. But then, Snape always did value dusty old books more than people's lives. Even his own.

"So you want me to break in?"

"Unnecessary. It happens that Shacklebolt's shift will overlap with Tonks's tomorrow."

Not for the first time, Sirius wanted to know where Snape was getting his information, stuck as he was in the Hogwarts dungeons, his eyes barely recovered enough to let him resume brewing, and taking no visitors that Sirius knew of.

"I suppose you have another list, or do I grab whatever looks most likely to strike me dead as soon as I lay a hand on it?"

Snape offered it to him. Like the other, it was a roll of parchment tied with a black ribbon.

"Great."

"It has also come to my attention that the Ministry plans an auction, once any Dark artifacts have been removed."

"How do you know these things?" Sirius asked, unable to help himself. Kingsley had relayed the news to the Order that morning, and to Sirius's knowledge he had left immediately after, speaking to no one else. Snape had not been at the meeting.

"It's what I do, Black." For a brief moment, it looked like Snape's temper was about to flare, but the next it was gone again beneath the emotionless mask. "What I want from you is quite simple. Take Draco to the auction and ensure he retrieves whatever of his possessions he might still want."

After a moment or two during which he pondered how such a request went any distance toward repaying a life debt, Sirius settled on shrugging. "Fine."

"It will be quite easy to get permission to take Draco out of Hogwarts," Snape continued, his voice carrying the sharpness of a challenge, "after you obtain legal guardianship."

Sirius stared at him with blank incomprehension.

"My own request was... denied."

"But --"

"You are his cousin, after all," Snape went on, ignoring him. "Scrimgeour does want to keep on your good side at the moment. And it is simpler to protect two children if both are in one place. The time and effort I'm expending on keeping the boy safe will be better spent on other things once that duty falls to you."

"I... see," Sirius finally managed. There was just about nobody he wanted to share his already crowded quarters with less than Lucius Malfoy's slimy spawn. And Harry would have a fit.

"Yes, well, see to it. I trust it won't be for very long, as Lucius won't leave custody of his son in your hands longer than absolutely necessary."

"Malfoy is in Azkaban."

"He's getting a new trial. We --"

"Oh no, we won't," Sirius said flatly, suddenly seeing very clearly where Snape was heading. "I'm not helping you get your Death Eater friends out of Azkaban."

"Lucius is not loyal to Voldemort," Snape said, momentarily silencing Sirius by the unexpected use of the name. "He hasn't been for years. If Dumbledore hadn't been a stubborn Gryffindor fool, half of Voldemort's supporters would never have rejoined him."

"Wait a bloody minute!" Sirius could barely speak through his indignation. "You can't say --"

"What, anything against Dumbledore? I assure you I can. And so will you, after viewing this."

A corked vial appeared out of another of Snape's pockets. It was filled with luminous liquid.

"What is it?"

"A memory. It's something you need to see anyway, as it concerns the horcruxes, but it will go a long way in knocking Dumbledore off the pedestal you have him on."

Sirius took the vial, but he couldn't stop glaring at Snape. "How can you? He trusted you. He gave you another chance, after everything you did."

"After everything I did?" An ugly half-smile twisted Snape's face, and his voice dropped low. "What did I do, Black? Something stupid when I was barely seventeen? I took one look around once I was on the inside, knew I wanted nothing to do with it, and spent the rest of my life paying for that mistake. I didn't need his sort of second chance."

Sirius realized belatedly that he had taken a step backward, away from Snape. "Why stay, then? Why stay and spy, and risk your life, if you didn't do it for Dumbledore?"

"I..." Snape's face twitched. There was almost nothing left of the impassive mask. "I blamed myself for Lily's death, and in that moment of self-loathing and knowing that I could never go back to the monster who killed her, I accepted a Vow to protect her child, not knowing how thoroughly it would trap me." With effort, Snape pulled himself together, his lips thinning as if he wanted to keep something back. "It's in the memory I've given you. You will see to what use he put that Vow."

Sirius looked down at the vial he was still holding. He didn't believe Snape, but he put it in his pocket, knowing he would have to look at the memory it held, if indeed it had anything to do with the horcruxes.

"Lucius is my friend," Snape said, his voice still low. His expression was impassive again, though his face a shade paler than before. "And we can use him on our side."

After that Snape said nothing else, and they stood in silence, each looking at the other with slightly narrowed eyes. Sirius was weighing his options and the possible consequences of refusing to do what Snape wanted, and he was certain Snape had planned for his refusal.

"Fine." He had to swallow, because the word and what he was agreeing to almost choked him. "But this is it. I'm not doing anything else, debt or no debt."

He turned on his heel, ready to walk out of Snape's room and yet knowing that wasn't the end of it. Snape wouldn't let that be the end.

"There is one other thing."

Sirius took a deep breath, forcing himself not to react. He stopped, not turning around. "I'm not doing anything else, Snape."

"I'm not asking for anything else. This is for Potter."

Sirius turned around then, and saw that Snape held another vial, this one filled with dark liquid. "What is it?"

"Something to slow the process. Perhaps even stop it altogether."

"You don't know?"

"It was difficult enough to find something that might work. Potter's case is singular."

Sirius hesitated for a moment longer, then reached for the vial. It felt warm and heavy in his hand. "And... you aren't going to change your mind?"

He didn't think he had ever seen such an ugly, derisive smile as quirked up the corners of Snape's mouth. "I don't want him, Black. You needn't worry. Feed him the potion and hope for the best. Chances are, he never even needs to know."