#12 Grimmauld Place, London, 1995

August had begun not so long ago, and Sirius Black had been stuck inside his old childhood home for a month now. It was majorly depressing, but he was cheered up slightly by the fact that Harry would be arriving tonight. They were preparing the Advance Guard now. Sirius wanted to be one of the Advance Guard, but of course that wasn't possible.

Sirius's mood was dampened just a little when he saw that Snape had come to give another report. Snape never stayed for meals, which Sirius appreciated. But Sirius tried to stay out of his way because Snape liked to needle him about his situation. It was rather like picking open a wound that had finally scabbed over, leaving it to bleed afresh…and then rubbing salt into it. But that wound, although it might scab, would never heal completely.

Speaking of wounds…Sirius felt guilty every time he looked at the actual, physical wounds left by Hedwig, Harry's owl. Harry had told her to peck him, Ron and Hermione until they wrote him decent letters—or, at least, that was what Sirius assumed. Being pecked by Hedwig was quite painful, but instead of making him angry at Harry, it just made Sirius wish he could write long letters.

Sirius was in the basement kitchen, examining his peck-wounds, when Snape walked in, alone; apparently he wanted a bite to eat before he left. Sirius glared at him, but didn't say anything. Snape was not so silent.

"How's the cleaning going?" he sneered.

"Mind your own business," Sirius snapped, scowling at him. "What are you going to eat? I'd suggest bacon—there's enough grease in your hair to cook a fair few slices."

"Reducing ourselves to petty insults, are we?" Snape's tone was still smug as he rummaged in the cabinets for food, passing over the bolted-shut ones.

"That's not a petty insult," said Sirius. "It's fact."

"Well, if we're talking appearances," said Snape, "I'm actually quite surprised you don't look more like the pig you are—considering how you spend your days sitting around like a potted plant, only less useful. Enjoying it, are you?"

"No, I'm NOT!" Sirius shouted, then paused. "Look…why are we fighting, anyway?"

"Um, because we hate each other?" said Snape, eyes narrowing.

"Yeah, but we're both miserable, aren't we?" said Sirius, putting his elbows on the table and sighing. "If you lived here, you would understand! You may have found a way to pay your dues, but it's not so easy for me to do the same."

"Fine," said Snape silkily. "If you think my life is so easy, you try living it."

"What do you mean?" Sirius demanded. "How could I possibly do that?"

"I've invented a new potion," Snape told him proudly. "Or at least improved an old one. It's called Everlasting Polyjuice Potion. Instead of wearing off after an hour, which is highly inconvenient, I've modified it so that you can stay in disguise for as long as you want, and you transform back by taking an antidote. I carry a vial of it around with me, just in case I need it. Do you hear what I'm saying?"

"Oh…I gotcha," said Sirius, and he couldn't help grinning. This probably wasn't a good idea, but it was better than being bored, and even Sirius himself would admit that he didn't really make good choices when it came to this sort of thing. So he agreed. Snape sneered again.

Snape poured the Everlasting Polyjuice Potion into two goblets. Snape explained that they could use anything with DNA, even spit, but they decided on the standard—hair. Sirius put his hair in one; it turned a sort of acid red. Snape did the same, and his turned the darkest black. Before they drank their potions, they set some "ground rules".

"We can switch back during the Christmas Holidays," said Snape. "I will provide the antidote then. But between then and now, we have to act exactly like each other. No one must know."

"When Harry comes tonight, you'll have to be nice to him," said Sirius, crossing his arms. "You have to call him by his first name, too."

"Well, you won't get to be so nice, and you have to call him by his last name," Snape said in reply. "By the way…when you get to my house, make sure you study Occlumency. There are books about it in my library. For if Dumbledore sends you on a mission, and the Dark Lord uses his Legilimency skills to find out that you are an imposter, you will be killed."

"I'll do it," said Sirius, knowing that he couldn't die…he couldn't die as long as Harry needed him. So he promised himself he would study Occlumency like he had never studied anything before. "For your part, remember that you're Public Enemy Number One, so you need to stay in here and not get yourself seen, or you'll receive the Kiss. That's what they're ordered to do if they find me. Now…do we trade wands or no?"

"We are taking on each other's appearances, not turning into each other," Snape told him. "Therefore, the wands will stay with their true masters."

"Very well, then," said Sirius. "Uhh…what about clothes? We can't be wearing each other's clothes when we transform. They won't fit."

"Hmm…" Snape was thinking. "Have you got a dressing gown?"

"Yes."

"Okay, you go change into that and give me your robes," said Snape. "I'll go transform in the nearest bathroom and once I look like you and have your robes on, I'll give you mine, and you can go change in your room."

Sirius's bedroom was on the very top floor, and the manor was many, many stories high, so he Apparated there to save time. Before long he had changed into his dressing gown and came back downstairs again with a crack, holding his robes in his arms.

"All of my robes are in my room on the top floor in the wardrobe," he said. "So you can wear them…you know, when you're me and I'm you. I assume your clothes are at your place?"

"Well, they are now," Snape told him. "But when you go to Hogwarts in less than a month, you have to pack everything."

"Naturally," said Sirius. "Okay…so go take the potion and turn into me, and when you get back give me your robes so I can take the potion and turn into you."