People were looking for an escaped convict that was a wizard. They weren't looking for an Animagus that could transform into a large dog. While the Forbidden Forest was prohibited, the passage of the Whomping Willow would allow someone small enough to run along and get to the Shrieking Shack, and from there straight into Hogwarts, or Hogsmeade, depending on the direction one took.
Hence, I knew really well what point of access Sirius Black was taking, and since I knew that, it didn't take me long to start staking the spot out.
"Mister Umbrus, have you taken an interest in gardening just recently?" it was Professor Sprout who queried me about my newly found taste for rose bushes, and as I smiled back at the matronly woman, I gave her a slightly hesitant nod.
"I just wanted to go with a flower motif for this year's Christmas gifts, professor," I said awkwardly. "I think that things like perfumes and whatnot would be more fitting, no?"
"Ah, it would be the age of prettying up, I suppose," the woman said with a glint in her eye. It was the dangerous glint of the savvy aunt that would slam her elbow in your ribs and give you a good ribbing while laughing amiably. I feared that glint just as much as I feared that matronly smile. It chilled my very spine.
Still, I was given permission to weed out some flowers which carried pretty smells, under strict supervision of Professor Sprout. That aside, I got my prize.
It was late, and the afternoon. The Whomping Willow was doing its damn best to whomp and stomp and chomp at the unseen breezes that dared tickle its branches, when my eyes caught a black blur between its roots slowly peeking its dog head out. I crouched amidst the bushes, shifting my body to hide as much as possible as I watched the large dog thing trot at a leisurely pace onto the grounds, headed for the secret passage beyond the hedgerows.
I emerged from my hiding spot faster than a lightning bolt, rushing forward and slamming the full brunt of a fully operational battle-stunner straight into the dog's flank, making it whine pitifully as it slumped on the ground, knocked out cold.
I breathed a sigh of relief, and tapped the unconscious dog to float it in the air, and then through the very same secret passage the dog had wanted to use. As much as it shamed me to admit it, I knew very well the way through the kitchens' secret passages, and actually didn't need much to convince the House Elves there that I wanted to bring my bestest new friend, the friendly Wooffo Doggo, all the way up to the Seventh floor unseen.
House Elf side-along apparition was something that would be better described as 'not something one wants to redo ever in his life', but it did the trick, and as I quickly got the Room of Requirements to open up to me, I carried the still unconscious dog right into the room. Funnily enough, a large amount of locks had been placed on the inner side of the door, as if to allow me to lock it properly up and prevent any further entrance.
It suited me just fine.
It was time to crack the mystery of the rabid Sirius Black, the One Wizard That Didn't Have A Brain, the guy whose brain cells died when grief overcame him. Still, I'd help him out. It was the proper thing to do.
I firmly pushed one of the book shelves onto the side of the door, preventing escape, and then I quietly tapped the dog with an Enervate, before bolting for the top of the desk. As expected, there was rabid barking and growling even as I kept my wand pointed in the dog's direction. "At ease," I said, "Be at ease mysterious dog that knows how to step inside and outside Hogwarts and was last seen escaping from the scene of the crime of harming the Fat Lady," I kept my eyes on the dog, his own throat emitting angry snarls. "If I wanted you captured, I'd have set the Dementors on you," I continued, "Or Hagrid, he'd have done it in the hope of getting Fang a new playmate, so please, enough growling."
The dog grumbled. It actually stared at me just as much as I stared back at him. "You could become something that can speak, you know," I continued, "We're inside Hogwarts, in the Room of Requirements. No one steps in here without my say so." Unless they had a battering ram and the desire to destroy the magically enhanced walls of Hogwarts, in which case I would probably answer with some form of anti-invader curse.
The dog showed its teeth, and then it slowly lurched up into a humanoid form. Finally, it became a human. His grey eyes looked at me even then, a mass of filthy, matted hair hung to his elbows. If eyes hadn't been shining out of the deep, dark sockets, he might have been a corpse. The waxy skin was stretched so tightly over the bones of his face, it looked like a skull. His yellow teeth were bared in a show of defiance, and I knew very well that while he might not kill me, he might just as easily knock me out and take my wand for his own purposes.
"You have successfully captured me, you cheeky little Ravenclaw, the terrifying Sirius Black, mass murderer," his grin was kind of maniacal, even as he made a mock bow, "I'd wonder what someone like you wants with someone like me, but I guess you're the kind of child prodigy that likes to gloat?"
"Actually, I thought you could use a bath and something solid to eat," I answered innocently enough. "Also, I'm reasonably sure the charges of murder are kind of false," I shrugged as I said that, much to Black's consternation, "If you really wanted to kill Harry Potter without concerns for your safety, it would be trifling easy to near him as a large, friendly dog, jump at his neck and snap it in half." I then inclined my head to the side, raising an eyebrow. "How about you settle down a bit, take a deep breath, and tell me the story of how everything went down?" just so I could finally have the background verified and be able to move the rightful accusations to the rightful people.
"You're an odd one, aren't you?" Sirius remarked.
I tapped with my open hand on the desk, and a bathtub appeared in a corner of the room with a divider. There was soap, and even fresh robes. "What do you want to eat?" I asked, "I'll have the house elves make it, and bring it up."
He stared at me as if I had grown a second head. Why were all the wizards I knew either staring as if I was some kind of Hydra, or wondering if I had gone mad? "You have no reason to believe me," Sirius said.
"Then I won't believe you," I answered, "I'll hear you out. I'll draw my own conclusions, formulate my own theories, verify them and then, finally, I'll make my informed decisions. But here's what I'm not going to do: I'm not going to give you to the Dementors, nor now nor ever. Those things are wrong, and I hate them." I grumbled. "If you are a cold blooded murderer of innocents, I'll knock you out, obliviate you, and then throw you in some kind of muggle prison. That will be more humane than a life sentence in Azkaban at the very least."
"Muggle prison?" Sirius emitted a bark-like laughter, "you want to make me believe that you'd just let me off like that? The betrayer of the Potters, the reason Harry Potter's without parents, the-"
"Your eyes," I said flatly, "Hold the same regret Headmaster Dumbledore's have," I grimaced. "It's the kind of eyes that belong to people who made mistakes. Grievous as those mistakes may be, the fact that you regret them is proof, at the very least, of some kind of moral fiber you possess. Maybe you didn't want to kill those muggles. Maybe you just wanted to kill someone else, or a stray spell hit something it wasn't supposed to hit-tell me the truth, Mister Black. I'll hear you out."
"Not like I got much of a choice now, do I?" Sirius grumbled.
"Maybe you don't," I acquiesced, "But I'm way more charming than the Dementors, and if you're innocent, or at the very least justified in what you're doing...I'll at least help you out. Though I'll warn you: no matter what, if you attempt to hurt the students, or the teachers, I will ensure you fail." I narrowed my eyes. "I'm protecting them all."
I knew that was the key to the entire deal. Sirius Black wouldn't make deals with slimy Slytherins, or prideful detectives. He would, however, accept those deals if they came from someone who had at heart the protection of the students. He'd make a deal with a Dumbledore-like existence, but no one else.
There was another bark-like laughter from the ex-prisoner of Azkaban, as if accepting the strangeness of the situation, but then he moved behind the divider and actually groaned blissfully as the hot water bubbled into the bathtub. Even though I was a kid, I still was the kid with a wand. If nothing else, he'd probably entertain me while waiting for his chance to escape.
The House Elves popped upon the desk some food, and thus as the man ate like a rabid beast, he explained his side of the story.
I smiled.
If he wanted to catch a rat, all one needed was the right amount of cheese.
And I, being the cheesiest of them all, had the best chances at getting the job done.