Disclaimer: Harry Potter is owned by JK Rowling, who is gracious enough to open her work up to the interpretation of the Internet.
A/N: Quick Reference
Before Hogwarts: Chapters 1-12
First Year: Chapters 13-41
Second Year: Chapters 42-61
Third Year: Chapters 62-81
Fourth Year: Chapters 82-112
Bonus Material: The World of The Accidental Animagus
Years 5-7: in the sequel, Animagus at War
With one beefy hand, a purple-faced Vernon Dursley pinned his nephew to the wall while smacking him across the face with the other. "I will not have any of your freakishness in my house, boy!" he bellowed, following it up with another smack.
Harry Potter's trouble had started before he could remember, but age five was quickly shaping up to be much worse than the previous four years. It had already been bad enough that he was made to sleep in a cupboard, wear his over-sized cousin's castoffs and do as many chores as he could handle. Somehow, going to primary school just made things worse. His aunt and uncle hadn't wanted to send him, but they knew they couldn't get away with keeping him at home, so they grumbled about taking time away from "earning his keep' and sent him away with Dudley. It took all of two days before his cousin and his friends invented their new favourite game of "Harry hunting," which they engaged in whenever the teachers weren't looking. It took all of four days before, while being scolded for a teacher for knocking over his juice (which Dudley had actually done), Harry was shocked to see the teacher's hair turn neon blue.
That evening was the first time Uncle Vernon had hit him himself instead of letting Dudley do it. Young Harry had no idea what was going on and only a vague idea of why he was in trouble. But he couldn't mistake his uncle ranting all night about his freakishness and vowing to "stamp that rubbish out."
Harry still had bruises a week later when the next strange, unexplainable thing happened. He didn't mind being locked in his cupboard too much most of the time. At least it kept his relatives away from him. But something had changed in him after that first beating. The urge to respond, suppressed by years of conditioning, started to assert itself again. Then, after being beat on some more by Dudley's gang at school and having his loudmouth cousin stomp on the stairs above his head one too many times, that urge crystallised into a single, overwhelming desire: escape.
"You're going to stay in your cupboard when you're told, boy!" Uncle Vernon's rant continued. "You're not to let yourself out unless we say so. Just like your good-for-nothing parents, always getting into trouble. Worthless, the lot of you!" He punctuated each sentence with either a slap to the face or a punch to the torso.
Harry's cupboard door had seemingly unlocked itself and flown open with a bang. Uncle Vernon had rushed over and slammed it shut before Harry could react, but it happened twice more right in front of him, at which point he was forcibly dragged out into the living room. As the beating began, Harry willed himself not to cry, but it was a losing battle, and as expected, it only enraged his uncle more. By now, he didn't even notice Aunt Petunia and Dudley standing by and scowling at him.
"Don't you cry at me, boy, or I'll give you something to cry about!"
With that last punch, Harry's crying jumped an octave. Then, the lights started flickering, and the doors and windows began to rattle.
"Vernon!" Aunt Petunia cried with a twinge of fear.
"Stop that! Stop that right now, you little freak!"
Harry kicked to try to get away, but his uncle held him too tight. Unseen by anyone, the lights began flipping on and off in all of the rooms at once. The floors began to vibrate.
"Daddy!" Dudley cried.
"Stop that this instant!"
As Harry's cries ascended to an inhuman yowl, every light bulb in the house exploded, every door slammed open, and all three Dursleys were thrown across the room and landed in a heap. When they came to their senses, Harry Potter was nowhere to be seen.
Vernon ran to the door, shouting, "Get back here, boy! Boy? I said get back here!" But there was no sign of his nephew. "He can't have got far," he said, finally lowering his voice. He saw the neighbours staring, now, drawn to the windows by the minor earthquake that had struck Privet Drive. Grumbling, he gave up and shut the door.
He did not notice a small black cat sitting in the bushes by the door—a cat with white feet, piercing green eyes, and a strange, white zigzag mark on its head. When he shut the door, the cat ran away down the street without looking back.
"Vernon, what happened?" Petunia asked in the half-destroyed living room.
"Little freak ran away, and I say let him go. They'll find him soon enough. I'll fix the lights tomorrow."
The Dursleys closed up the house and took an uneasy dinner by candlelight. They sincerely hoped that their troubles were over for the time being, but they would be visited by strangeness twice more that evening.
With the first visit, two Ministry of Magic Obliviators appeared at the door and stunned the Dursleys before they could even get a word in. There was no sign of any wizards wandering around the neighbourhood, and the Trace showed no underage magic users on the premises, so the Ministry had concluded the magical discharge at 4 Privett Drive was caused by a passing troublemaker. The Obliviators repaired the damaged light fixtures, set right the overturned furniture, mended the splinters broken from the doors, and wiped all memory of the incident from the Dursleys' minds.
They cast a warming charm on the food just before they rennervated the family, so that not even the smallest detail was out of place. They left without even looking at the cupboard under the stairs, and the Dursleys awoke thinking nothing unusual had happened.
The other visitor that evening wore a purple robe and a long, white beard. Albus Dumbledore was more worried than he had been in years when he knocked on the door on Number 4. Even from the outside, a quick detection charm told him that Harry Potter was not in the house.
A tall, lanky, horse-faced woman opened the door to the shock of her life. "You!" she shouted. "What are you doing here?"
"A pleasure to see you, too, Petunia," Dumbledore said flatly.
"Who is it Petunia?" Vernon called.
"It's that freak who left the boy with us."
"What?" Vernon barged to the door. "You! You can have that boy back. We never wanted him in the first place."
Dumbledore's eyebrows shot up at this. The Dursleys seemed to be even more unfriendly than he expected, and the large man was gearing up for a serious rant. He cut him off quickly by saying, "Where is the boy?"
"He's right…" Vernon stopped. The boy was supposed to be in his cupboard, but not only could he not get away with saying that, for some reason he didn't think it was true. He tried to think over what had happened that evening. It was coming back a blur but he managed to recall one true fact: "The boy ran away this afternoon. Just took off down the street, couldn't keep up with him. And I say good riddance. Let someone else take care of him for a change."
"And you just let him go off on his own?"
"Yes. He's been nothing by trouble from the start…"
Dumbledore tuned out the rant. From their behaviour, something was definitely not right. He took a peek inside the two adult Dursleys' minds, but he didn't have to look far to find an answer, though he wished he hadn't: telltale signs of obliviation, and what looked like a pretty lousy job of it, too. Something horrible had happened here and been shoddily covered up.
"…and I won't tolerate any more of his freakishness!"
"Enough!" Dumbledore shouted before stunning all three of them. Casting a new memory charm to cover the old one, he instructed them: "You are very concerned because your nephew ran away. You will contact the authorities immediately. You will ask Arabella Figg to keep an eye out for him, and you will inform her at once when he is found. You will not remember my visit tonight." When he was done, he hit them with a delayed Rennervate that gave him just enough time to step outside the property line and apparate to the gates of Hogwarts.
Minerva McGonagall entered the Headmaster's office to find him bent over some of his many devices with a frown, muttering incantations, with a look in his eyes that was darker than any she had seen in years. "Albus, what's wrong?" she asked. "You said it was urgent."
Albus looked up. "Oh, Minerva, I fear something terrible has just happened," he said. "I have reason to believe that Harry Potter has been taken."
"What?" Minerva stumbled in shock, but managed to sit herself down. "Taken? How?"
"This afternoon, he dropped off my trackers entirely. They indicate that he is still alive, but I cannot find him anywhere."
"You can't find him? But what could do such a thing?"
"To block my tracking charms would require the boy to be hidden behind very powerful wards that I am not keyed into, possibly a Fidelius Charm. I've just returned from his relatives' house. They claimed that he had run away, but in their minds, I saw obvious signs of obliviation."
Minerva put the pieces together. "Someone, somehow, got through your wards, kidnapped him, hid him behind these other wards, and obliviated his relatives. And because they didn't involve you…"
Albus nodded grimly. "We can only assume that their intent is nefarious."
She shot to her feet. "We must find him, Albus!"
"Yes, we must," he agreed, "but it must be done discreetly. We cannot risk panicking the public or tipping our own hand."
"But the boy…"
"Is still alive for the time being, which suggests that their intent is not to kill him. I also saw no indication that the blood wards had been breached, so whoever actually took him did not mean overt harm. We must begin investigating places and individuals who would have access to those kinds of wards, but we cannot allow the boy's enemies to know he is missing. That would be an even greater disaster."
Minerva sank back down in her seat. "I suppose you're right, Albus. I'll begin looking with what little time I can spare."
"Thank you, Minerva. I will do the same."
Harry Potter, at that moment, was wandering the streets of Little Whinging, very confused. He was happy to have got away from his relatives, but he had no idea how he had done it. From the fur and tail, he could tell that he had been turned into some kind of animal. It wasn't until he managed to see a distorted reflection in a car hubcap that he figured out that that animal was a cat. He didn't know how he could have turned into a cat, nor did he know how to change back, but he could guess that it had something to do with the "freakishness' his uncle had been shouting about, and he decided to get farther away before trying.
Adding to his confusion were the strange sensations that accompanied being a cat. He could see amazingly well in the fading light. His whiskers tickled his face with the slightest breeze. He was surrounded by high pitched squeaks and chirps that he had never noticed before. But the most disorienting part was the smells. He was bombarded by dozens of unfamiliar smells, some of them completely overpowering to his human mind, but all sensed individually. He could only identify a few of them—the most prevalent were the grass, the dirt, and the autumn leaves—but there were many others, trails presumably left by animals, by people, by passing cars, all subtly different in ways he couldn't explain.
Harry must have looked a rather strange cat, wandering back and forth across the yards, stopping every few steps, looking all around, and sometimes turning around before moving on as he tried to take in everything about the world around him. He quickly got turned around doing this, and he had only made it a few blocks before he had got thoroughly lost.
While he didn't care about being able to find his aunt and uncle's house again, he presently realised that he was quite hungry, and thirsty, not to mention sore from the beating he had received, and he didn't know how to deal with any of those things as a cat.
Water wasn't that hard to find. He wasn't used to drinking water from anything but a glass or a garden hose, but enough people in Little Whinging had ponds or pools or fountains, and he wasn't about to be picky. He came to the first small pond he found, and he was surprised to learn that one of the scents he could now smell was that of water. He was reasonably sure water didn't have a smell as a human. With a little practice, he was able to lap up the water like he had seen cats do in pictures.
Food was harder to find. Harry knew that cats were supposed to eat mice, but he didn't know how to catch mice, and he wasn't sure he could actually eat one if he did. He'd also heard of people feeding stray cats that showed up on their porches. He decided to try pawing at the back door of the house with the pond, only to find himself faced with a woman who acted disturbingly like his Aunt Petunia and shooed him away with a broom. Running away in fright, he resolved to find some other source of food.
He saw a couple of other cats and tried to follow them, hoping they knew where to find food, but they hissed at him when he got too close. But they had to eat, too, so there must be food somewhere nearby. After a while, he decided that since his cat's nose could smell water, maybe he could follow it to some food. He sniffed the air and got a whiff of a bunch of smells, some of which, though he didn't know why, did smell tasty. Haltingly, he followed one trail to an open rubbish bin. After scaring away a squirrel that had dived into it, he investigated. The smell of rot was overwhelming, but he could tell that part was coming from further down. He found some table scraps on top, even some meat. They were dirty, but not rotten. He grabbed a big chunk of half-eaten chicken with his teeth and dragged it far enough away that he could stand the smell. After four years of table scraps, it wasn't much worse than he was used to. Holding it with his paws, he dug in and was surprised how easily the chicken came apart in his sharp teeth.
A little while later, Harry found a warm spot to curl up in (unbeknownst to him, on the other side of a wall from a poorly-insulated water heater) and went to sleep. It had been a hard start, but he began to think that he would enjoy being a cat more than being a human trapped at the Dursleys' house.