The castle came into view over the tops of the trees late on the afternoon of the next day. Something stirred within him at the sight of his first true home. Within a couple of hours, he sighted the castle gates with their cold, inhuman guards. He was going to have to go right past them in order to get in. It took him nearly half an hour of crouching in the bushes to work up the nerve to approach. In the end, he took a deep breath, fixed his eyes upon the castle beyond the Dementors, and passed between them at a steady trot. They did not spare him more than an incurious glance.

Heaving a sigh of relief, he stopped several paces beyond the gates, and looked around. From this distance, the only smells that came to him were those of the Forbidden Forest. Good enough. That would be a reasonably safe place for him to lie hidden while he formulated a plan to get into the castle and see about a certain rat.

He padded around the edge of the grounds, keeping to the wall until the trees began, then ducking into the safety of their shade. He passed the Whomping Willow, swaying gently in the early autumn breeze, and wondered idly if he could find a way to prod the secret knot in his current form. The Shrieking Shack would undoubtedly make a fine hideout. Although less so, if he broke half his bones getting there.

He was not far past the Whomping Willow when the first familiar scents assailed him. He stopped and sniffed again before starting slowly forward. There. Just at the edge of the forest, about fifty paces away, stood a lumpy, familiar-looking hut.

Hagrid, he thought. Hagrid is still here.

The realisation gave him decidedly mixed feelings. On the one hand, Hagrid was the one who had taken Harry from him on that dreadful night. Not really his fault, but still - On the other hand, Hagrid had been a sort of friend, and was a kindly man, who loved animals - the bigger and more vicious, the better. Sirius bared his teeth in a growl that was half a laugh. It was an idea.

Moving through the trees, he was able to approach fairly near the hut without being seen. And there was Hagrid, looking much as he ever had - the same moleskin coat, the same long, tangled beard, the same good-natured voice with its own ideas about the English language. And he was - teaching? Sirius sat back on his haunches in surprise. It looked very much as though Hagrid was leading a Care of Magical Creatures class. Sirius wondered what had happened to old Professor Kettleburn.

He sniffed hopefully, but Harry was not in this class. These were older children, possibly fifth or sixth year students. They looked decidedly dubious about their teacher's abilities.

"Come closer," Hagrid was saying, "they won' hurt yeh."

But the deep roar which followed these words suggested to the students that perhaps the more prudent course of action was to back hastily away. Hagrid looked worried.

Sirius waited until the end of the lesson, during which Hagrid utterly failed to get any of his pupils to approach the crate, before he decided it was safe to leave the cover of the trees.

"On'y manticore cubs," Hagrid was mumbling grumpily to himself. "Thought th' kids'd like 'em. They're cute little blighters an' all."

Sirius waited patiently on the hut steps, tongue out, the very picture of canine joviality. At last, Hagrid turned and noticed his audience.

"Hallo there, wee dog," he said, holding out his knuckles to be sniffed. Sirius politely accepted the invitation. "Lost, are yeh? Well, ye've come ter the righ' place." He held open the door. "Come in an' meet th' boys."

The boys?

From Hagrid, that could mean anything from fluffy, harmless puffskeins up to full-grown hellhounds, with the latter being far more likely. Sirius peered cautiously into the hut. A large boarhound stopped mid-bound at the sight of him, and cocked his massive head with a sharp whine, as if to say, "Friend or foe?" Sirius whined in return, and let his tongue loll out some more, which he found usually stood him in good stead with other dogs.

"It's alrigh', Fang," said Hagrid indulgently, scratching the big dog behind the ears. "This pooch is jus' 'ere for supper. Beaky, come an' meet our new friend."

A strange, birdlike quark came from the shadows beside the stove, and into the middle of the room stepped a large creature with not a few sharp points. Sirius's first instinct was to crouch behind Hagrid, knowing the kinds of things Hagrid considered to be harmless house pets.

"He won' hurt yeh," Hagrid told him. "Beaky's jus' stayin' here a while until we get some matters wi' th' Ministry cleared up. Ah, yer a friendly brute, aren't yeh?" he said fondly, turning to the creature called Beaky.

This all sounded fairly ominous to Sirius, but he tentatively wagged his tail, and the Hippogriff consented to sniff him in a reasonably benign manner before returning to his corner to gnaw on a very large bone.

Sirius realised Hagrid was looking at him thoughtfully. "Yeh know, there used ter be a dog jus' like you hung around here, oh, ages ago." Then he grinned. "Ah, but that would be back before you or Fang or Beaky was ever born. I'm gettin' old. Jus' listen ter me!" he said, tying on an enormous floral apron.

Hagrid was bending over the stove, humming to himself, when there came a scratching sound at the door.

"We have another guest fer tea!" he exclaimed, rubbing his hands together.

When the door was opened, in stalked the ugliest cat Sirius had ever seen. He was ginger, excessively fluffy, and had a face that suggested he had seen a few brick walls up close. The creature eyed Sirius dispassionately, and Sirius got the impression that the cat was not fooled by his disguise in the slightest.

"Here, Pooch," Hagrid was saying. "This is Crookshanks. He's Hermione's friend. Likes ter play at bein' a cat. Well, we'll keep his little secret, won' we?" He chuckled good-naturedly.

The not-a-cat apparently decided Sirius was harmless enough, and ignored him in favour of twining himself about Hagrid's ankles, shamelessly begging for scraps. Sirius, on the other hand, gazed thoughtfully at the creature.

Hermione's friend, eh? he thought.

He had no idea who Hermione might be, but chances were that she - and presumably this furry friend of hers - resided in the castle. Human friends were not going to be much help. The four-legged variety, on the other hand -

Sirius knew that being on good terms with Hagrid and his non-human friends was likely to be the key to finding Peter inside the vast castle of Hogwarts, so he cultivated those friendships. More often than not over the following days, tea time found him in the hut, sharing a meal with Hagrid, Fang, Buckbeak and whatever other "friends" Hagrid had visiting that evening.

It was from Hagrid that Sirius learned Dumbledore still presided over Hogwarts, and that Harry was in Gryffindor, as well as some of the more surprising adventures Harry and his friends had had since they began at the school. Sirius was grateful for Hagrid's habit of talking to all animals as if they could understand.

Hagrid, it seemed, was on very friendly terms with Harry, which meant Sirius would have to be careful. Harry had seen him in Little Whinging, and if he saw him again, he might put two and two together, so he carefully avoided the hut any time he smelled human guests present. He usually hid deep in the forest during the Care of Magical Creatures lessons, since occasionally these classes penetrated the forest's perimeter.

Because of these habits, it was not until his third week at the school that he learned about Ron Weasley. He had forgotten that there was a lesson that afternoon, and did not have time to slink out of the hut and into the trees without being seen, so he decided to stay and watch the lesson surreptitiously through the window.

"Want ter go out, boy?" Hagrid asked him, holding the door open, but Sirius stayed where he was. Hagrid shrugged and went back to feeding Buckbeak.

Harry was in this class. Sirius saw him as soon as he came out of the castle, walking between a tall, red-haired boy and a girl with bushy brown hair. The three were talking and laughing, and Sirius felt his chest tighten to see that Harry clearly had at least two close friends. His own friendships, after all, were what had made Hogwarts the best time of his life.

Hagrid had just opened the door again to go and join his students, when Sirius saw the rat. A nose, whiskers, and two tiny pink paws, one missing a little rat toe, peaked out of the pocket of the tall, red-haired boy's robes.

There he was, bold as you please - the cause of all the misery, anguish, and torment Sirius had suffered for more than a decade.

Sirius snarled and leapt for the door, but as he passed, Hagrid, with amazing presence of mind, grabbed him by the scruff of the neck and hurled him back into the hut. He yelped as he bounced off a chair.

"None of that, Pooch," Hagrid admonished. "They're nice kids out there. Don' you give 'em no trouble."

With that, he turned on his heel and closed the door behind him. Sirius was just about to slip forms, risking all to go after him, when he heard the key scrape in the lock. He was trapped. And Harry was out there with the rat.

He returned to the window and stared fixedly at the children. Gradually, he managed to relax a little. Harry and the red-haired boy were clearly friends, and if Peter had not made his move before now, there was no reason why he should do so today. Harry was likely in no immediate danger. Still, he watched for any further sign of emerging whiskers, but apparently Peter had decided that Hagrid's Care of Magical Creatures class would be a poor place to show himself. Many of Hagrid's favourite creatures would likely find rat a tasty treat.

Six weeks into the term, Sirius was still no nearer to finding a safe way into the castle. The only time he saw Harry and his friends was during their lessons with Hagrid, but now Hagrid was wary of him around the children, and kept him locked up in the hut until all the students were safely back at the castle.

He watched these lessons with growing anxiety. What if Peter caught a whiff of him with that sharp little nose? Surely by now he must know that Sirius was looking for him. Sirius's own presence was putting Harry in greater danger than ever, and every day he waited to make his move was one day closer to "too late".

What he really needed was a state of disruption at the school; a time when people's minds would be fixed on something other than himself. He tried desperately to remember what special occasions were celebrated on the Hogwarts calendar. He sat with his muzzle on his paws, gazing between the trees at the gray, autumn sky. No help there. But when he lowered his eyes, they fell upon Hagrid's vegetable garden, which, at this time of year, was filled with giant pumpkins.

How could he have forgotten Halloween? Granted, for a dozen years, he had had no calendar available to him, and no cause to celebrate, but Halloween had been one of the great Marauder holidays. He and James had almost always come up with some ingenious prank to celebrate, and they had had an unofficial annual competition to try and make McGonagall laugh at their choice of costumes.

Halloween would be perfect. Not only was there the feast, but there would be the traditional Hogsmeade weekend, when half the students and staff would be down in the village. If he wanted to slip into the school unnoticed, that was surely the time to do it.

It was a good plan, he decided. He was ready. How could it possibly go wrong?