A shout out to my four reviewers- thank you! It's nice to know that people are enjoying the story. Seeing as I have a good idea of where I'm going with this, I'm going to TRY to keep to some sort of schedule. I'm going to attempt to update once a week, on either Saturday or Sunday. This is, of course, tentative, but watch specifically for those days!

As a dog, Sirius noticed a lot more than he would while as a human.

This observation went unnoticed in Azkaban; that horrid place almost required him to let go of every aspect of his being. But in the quiet of Dumbledore's office, he looked to the old man and saw things he hadn't seen before. The headmaster was shaking just a bit, and though it would probably have not been seen by anyone, Sirius could tell. Dogs were always keyed in to those sorts of things.

Dumbledore's face also expressed an emotion that confused the furry dog at first, but what was soon slowly understood. There was a hint of disbelief on his face-no-a wanting not to believe. For just a moment, Sirius wondered why Dumbledore would rather he be Regulus, but then thought of what the professor must have seen. Sirius knew that he looked sad, disheveled, and as if he had been through hell and back. Albus Dumbledore would most likely be able to guess at where his sad eyes came from, and that almost made Sirius a little bit pleased. Dumbledore wanted him to be Regulus, because he couldn't believe that Sirius Black would turn his back on James Potter, his best friend, and get involved in the dark arts that his family is known for. And in such a way that would get him thrown into Azkaban.

He could also tell that Albus knew about his Animagus form, from the way he slowly sagged back into his chair. Sirius hadn't been sure, but something that Dumbledore had said during Harry's Fourth Year had left a mark.

Sirius was angry.

Really angry.

"How could you let this happen, Dumbledore? You knew something was wrong, and yet you did nothing about it! Harry could have died! He almost did!" Sirius yelled, his voice vibrating throughout the hallway.

He had only been alone with Dumbledore once that year, before the big Barty Crouch Junior reveal. He certainly had enough time to get his anger out when with Harry in Dumbledore's office, but he didn't want to make Harry tired or uncomfortable by blowing up at Dumbeldore for allowing a Death Eater in the school. Now, for some reason, after ordering Sirius to leave and warn the members of the Order, Dumbledore quickly stopped him for a "talk." If he suspected for one minute that Sirius wouldn't be upset, he had another thing coming.

"Calm yourself, Sirius." Dumbledore encouraged. "Harry is safe, and isn't that all that matters?" Sirius tried to say something back, but Dumbledore added, "And I suggest you keep your voice down. The Weasleys aren't the only ones who are perhaps still awake."

That kept Sirius quiet for a bit, but he turned his back on Dumbledore and began pacing across the length of the hall.

"I just keep thinking, just, what if he did die?" Sirius rambled quietly, as his voice started shaking. "What would James and Lily do if they knew that I had let him die? Harry would be dead, and they would never forgive me. I have to protect him, I have to-"

"Sirius," Dumbledore said, though his own voice was forceful enough to halt Sirius from his pacing. Sirius looked at Dumbledore with sad, broken eyes, and wondered why Dumbledore had asked him to stop in the first place. He was about to leave the grounds to go hang low with Remus for a while, just as he was ordered to do. What could Dumbledore possibly have to say that could be so important?

"Listen closely, Sirius." Dumbledore said, looking directly at him. "I've made many mistakes in my life. I have many regrets. If I'm going to be honest, not figuring out that you were an innocent man is one of the top regrets on my list."

Sirius was confused. "Why are you telling me this now, Dumbledore? What does this have to do with Harry?"

Dumbledore walked over to Sirius and placed his hand on the man's shoulder. "You're some of the only family Harry has left. He needs you now more than ever." Dumbledore smiled sadly. "And I bring up my regrets to tell you not to fret over this turn of events. There are many more things a man can regret, and this is not one of them. You're a loyal man, Sirius, and I could tell that you were blaming yourself for what happened." Dumbledore smiled. "How I did not see that a dog is obviously more loyal than a rat, I'll never know. I know now that you'd never willingly leave him, but stay safe. For Harry."

Sirius was touched at Dumbledore's trust in him, but one thing did strike him as odd. "Wait, you knew about our transformations when I was in Azkaban? When the hell did you figure that one out?"

Dumbledore only chuckled. "Oh, you'll find that I have many ways of finding things out, Mr. Black." Before Sirius could speak again, Dumbledore quickly turned his back and began walking towards where the Diggorys were waiting, his cryptic response hanging in the air.

"Remember Sirius, find the old crowd. But of course, I understand if your nose isn't up to it anymore."

Taking that as a challenge, Sirius transformed again and bounded away, wondering just how long Dumbledore had known about his Animagus form.

Well, it was before my seventh year Sirius thought to himself, observing how Dumbledore was watching him.

Taking his head out of his hands, Dumbledore looked at the dog before him and said quietly, "You can transform back now, Mr. Black. I believe you."

Jumping up onto his back legs, Sirius transformed back and sat back down across from Dumbledore, reveling in how familiar this scene was. Except there was no Harry to burst in and explain what happened during the third task, and that made Sirius feel an aching emptiness inside his chest.

"So, seeing as I'm not exactly used to this whole 'time travel' thing, I was wondering what happens now?" Sirius asked, his curiosity not hidden in his wondering tone.

Dumbledore contemplated for about a minute, and then said finally, "I met a man who traveled through time many years ago."

Sirius perked up. "That's great! Where can I talk to him?"

"He's dead."

"Oh."

Silence cascaded throughout the room once more. Sirius was growing fed up with the lack of actual information, and asked, "Did he say anything helpful about time travel? Anything that could help me at all?"

"Well," Dumbledore responded, "It would help if I knew how you came to be here. How exactly did you end up falling out of the Mirror?"

Sirius relayed everything that had happened that day, making sure not to include any names or the reason he had been at the Department of Mysteries. He simply said "I was there, and that's all you need to know." He talked about falling through the veil, and the feelings of despair and emptiness that encased him. He told Dumbledore about seeing the Philosopher's Stone, and he knew Dumbledore was surprised that Sirius knew what it was from the way he clutched the stone tighter to his chest. Finally, he told Dumbledore about making a grab for the stone, and then falling right into the Headmaster's office.

"And that's how I ended up here." Sirius finished. "So, from that, is there anything that you know, or am I just stuck here, because if that's the case then-"

"I have a theory." Dumbledore interrupted, comprehension dawning in his old eyes. "Two actually."

Sirius motioned him to continue, and so he did. "My first theory is that you truly have gone backwards in time. That would mean that you're in the same timeline as the one you left." He paused, trying to find words to express what that implied. "I see it, Sirius. In your eyes. Some things have happened that you would want to change, am I correct?" Sirius nodded vigorously. "If that's the case, then I'm afraid that in the first scenario, you can not change anything. If something were to change, terrible things would happen. It's as you said, bad things happen to wizards who meddle with time."

Sirius deflated a bit, but at the same time a suspicious gleam took root. "And the second theory?"

Dumbledore leaned back, trying to explain what he was thinking in the best way he could. "The second theory is based off of my experience with the other time traveler that I've come across. He didn't necessarily travel through time; he traveled to a different timeline, one that differed slightly from the one he came from, but only slightly." At Sirius' confused look, Dumbledore began to explain more in depth. "For example, say in timeline A, a certain potion was created in the early nineteenth century. Then, in timeline B, this potion was not created in the early nineteenth century. In fact, it hadn't been created at all."

Sirius smirked. "I see that this is an example from experience?" He paused, thinking of the implications. "What was this potion called, if I may ask?"

Dumbledore, guessing the same thing, replied, "The Pepperup Potion."

Sirius grew excited. He dared to hope. "Is that the one that exists in the other timeline?"

"No. It exists here."

Sirius sagged his head in defeat. "So, in your time traveler friend's world, that potion didn't exist?"

Dumbledore must have sensed that that was not the answer that Sirius wanted to hear, and sadly replied "No, it did not. That's how we knew that our worlds were different."

"So, if we can find one factor that differs between our timelines-"

"-then you'd be safe to intervene." Dumbledore finished. "However, since we don't know anything yet, I suggest we keep you hidden here until we know for sure. School will be starting in just a few weeks, and I'd rather keep you from your past self if that can be helped."

Sirius smiled, and asked, "Could we compare things now, if that isn't too much to ask?"

Dumbledore sighed. "I was hoping to get to sleep early tonight, but the idea that a stranger may have information not privy to me is intriguing. Let's begin."

They spent the next ten days talking about their worlds. Potions, spells, history. Sirius' life and his friendship with the other Marauders. The only thing that they could find that could be different was the situation with the Mirror of Erised. Sirius had mentioned that Dumbledore had hidden the stone there in 1991. However, he did not have any proof that Dumbledore hadn't tested it years before, so that point was declared moot.

After the end of the tenth day, Sirius was growing tired. He felt cooped up again, never able to show his face around the castle for fear of getting caught by the professors. It reminded him too much of his time at Grimmauld Place which, in turn, reminded him of Harry. He wondered what Harry and Remus were thinking. He wondered how long he had been gone for.

It was late at night, and he decided that he needed to go to the bathroom before bed, but he was too tired to keep track of where he was going. Making sure to avoid Filch, he wandered throughout the castle and found the first bathroom he saw. Not caring whether or not it was meant for boys or girls, he went inside.

After relieving himself, he became more aware of where he was and cursed himself for his stupidity. He was in the first-floor girls' bathroom.

Otherwise known as Myrtle's bathroom.

Hoping to get away as quickly as possible, he almost made it to the door when he heard a female's voice ask, "Who in the world are you, and what are you doing in my bathroom?"

A/N For those of you wondering about the two theories, here's a clearer rundown:

Theory 1: The time travel from the third book. Harry and Hermione could not directly intervene because they were in the same timeline. Anything they did would affect their own future.

Theory 2: This one is a little harder to explain. Let's say that there's two timelines. They are exactly the same, except that in one, the Harry Potter series was never written (a tragedy, I know). Therefore, if someone were to travel from our world to the world without Harry Potter (let's say to 2004), then they could make changes because the worlds, though very similar, are not the same. The outcome of the changes would not affect the time traveler. If that's still not completely understood, then the simple way to put it is that if this theory is correct, Sirius can make changes to the timeline and not have it affect him or the canon world, just the world he's found himself in.

Thanks for reading!

~M