Disclaimer: J.K. Rowling owns all the characters and the HP universe. Which is why she's making money off it and I'm not.

Big thanks to my intrepid beta readers, Narcissus and Nymphica. Don't know what I'd do without you guys.

Harry Potter and the Polka Dot Plague
By Mariner

Chapter 1 -- An Inauspicious Arrival

For the first time in four years, Harry Potter felt dejected as he pushed his baggage trolley through the divider between Platforms 9 and 10 in King's Cross Station. Under normal circumstances, he looked forward to the start of school with an enthusiasm rarely found in adolescent boys. School meant an escape from the Dursleys, and even with all the dangers and injuries that tended to plague him every year, Harry had always thought that Hogwarts was still a huge improvement over Privet Drive.

But that had all changed last year, at the end of the Triwizard Tournament. Voldemort was back. Cedric Diggory was dead. And no matter how many people tried to tell him otherwise, Harry knew that it was his fault. If only he hadn't kept Sirius and Professor Lupin from killing Wormtail when they had the chance… if only he hadn't offered to share the Triwizard victory with Cedric… Regrets and recriminations had filled Harry's head all summer. He had spent most of his time in his room, feeling too depressed to face the world beyond his door. Thankfully, the Dursleys had mostly left him alone. Uncle Vernon and Aunt Petunia had ceased bullying him ever since Harry had convinced them that the notorious murderer Sirius Black was looking out for his welfare, but they didn't want to be bothered with him, either. So if Harry wanted to sit quietly in his room all day, they were content to let him. Dudley had made himself obnoxious for a while, but Harry couldn't find the energy to care, and eventually his cousin had grown bored with Harry's lack of response and waddled off.

Harry had not left Privet Drive at all until the day before, when he'd gone to Diagon Alley with Ron and Hermione to shop for school supplies. The Grangers had picked him up in their car. Hermione's parents were respectable Muggle dentists, and looked it, so Uncle Vernon had been grudgingly civil to them, even if he did squint his beady little eyes at Hermione as if he expected her to sprout horns and a tail at any moment.

Hermione herself had given Harry a concerned frown as he climbed into the car.

"Are you all right, Harry? You look terribly tired. I hope you haven't been studying too hard."

Coming from Hermione, that was downright hilarious, but Harry was in no mood to laugh. In truth, he hadn't studied at all, even though all his teachers had assigned loads of homework over the summer in order to start getting the Fifth-years ready for their O.W.L.s. He knew he should be worried about all the books left unread and essays left unwritten, but somehow he wasn't.

Ron was even less diplomatic than Hermione. "Blimey, Harry, you look awful! Haven't those Muggles been feeding you all summer?"

"I'm fine," Harry muttered, feeling self-conscious and irritable. The other Weasleys were giving him concerned looks too; Mrs. Weasley, in particular, looked as if she was getting ready to fuss. Harry hated being fussed over. So he summoned up a smile and determined to act cheerful for the rest of the day.

He managed it, but it was very tiring. Even now, after a good night's sleep and a huge breakfast at the Burrow, Harry was still tired. To top it all off, he was starting to feel distinctly queasy. Harry suspected it was the breakfast. He really hadn't felt hungry when he woke up, but Mrs. Weasley had looked so concerned when he tried to refuse her offer of food that he quickly recanted and choked down nearly half the eggs, rolls and sausages she piled on his plate. Now it had all settled into a big greasy lump in the bottom of Harry's stomach, and all he wanted was to curl up in his seat and go to sleep for the duration of the train ride.

It didn't work out that way, of course. They had claimed a compartment to themselves as usual, and Harry had quickly claimed a corner seat for himself, but peace and quiet were not to be had. Fred and George came in twice, and managed to make something explode each time. They also made loud and boisterous fun of Hermione's Prefect badge (she took it with much better humor than Percy had). Draco Malfoy stuck his head in once, flanked by the ever-present Crabbe and Goyle, but left in haste when Hermione told him she'd been reading up on transfiguring people into ferrets. Neville wandered in looking for his toad, Lee Jordan wanted to talk about Gryffindor's chances for the Quidditch Cup without Oliver Wood… and every single person (except Malfoy and his goons, of course) had something to say about how awful Harry looked. It was very irritating.

It was the longest train ride ever. And after that there was the carriage ride, and the walk to the Great Hall, and the endless milling around while waiting for Professor McGonagall to herd the First-Years in for the sorting. After a few minutes, Harry elbowed Hermione in the side.

"Listen, could you tell me the password? I'm going to go up to the dorm and lie down."

"What?" Ron gaped at him. "Are you crazy? You'll miss the Sorting! And the feast!"

"We've missed the Sorting before and nothing terrible happened," Harry pointed out. "And I'm not hungry. I just want a nap."

"Are you sure you're all right?" Hermione was frowning at him again. "Maybe you should go see Madam Pomfrey."

"I'm fine," Harry repeated for the thousandth time that day. "I just need a nap, that's all. Tell Professor McGonagall after she's done with the Sorting, will you? I don't want her thinking I've snuck off to get into trouble."

"I'll come with you," Ron offered, but Harry shook his head.

"No, you stay. Tell me what the Hat sings."

Hermione still looked dubious, but she did tell him the password without further protest. Harry thanked her and elbowed his way out of the room. The paintings in the corridors turned to look at him as he went by, and Harry could've sworn he heard one of them - a portrait of a motherly old witch in a rocking chair - murmur something about him looking unwell. He quickened his pace, but that just tired him out so that he had to stop and catch his breath when he was halfway there.

"Mister Potter." A smooth voice hissed into Harry's ear, causing him to nearly jump out of his skin. He spun around to find his least favorite professor hovering over him like a particularly ill-tempered vulture. "And what might you be doing out here?"

Harry fought down a groan. Of all the people at Hogwarts, Severus Snape was the last one he wanted to see just now. The man seemed to live for the sole purpose of getting Harry into trouble. He had an amazing ability to sneak up on people without their noticing, and to always pop up at the worst possible moment. Harry supposed it was a useful skill for a spy. Snape had spied on the Death Eaters for Dumbledore in the last war, and was apparently doing it again now. If it had been anyone else, Harry would've admired them for it, but no amount of effort was going to make him admire Severus Snape.

He stood up straighter and tried his best to look innocent of any wrongdoing. Somehow, the fact that he actually was innocent for a change didn't make the task any easier.

"Nothing," he managed to say finally. "I'm not doing anything."

"Nothing?" Snape's mouth curled into a familiar sneer. "I find that hard to believe. At the very least, you're breathing and taking up space. And I, for one, would like to know what else you're up to."

"Nothing," Harry repeated doggedly. "I was just going to the dorm to lie down, that's all."

"Indeed." The sneer grew more pronounced. "The Sorting and the feast are not providing sufficient entertainment for famous Potter?"

"No! I mean, that's not why I left." Harry rolled his eyes, though he knew it would only make Snape more annoyed. No matter what he did, the Potions master always managed to interpret it as a sign of arrogance. Harry winced, aware that what he was about to say sounded very much like a lame excuse, but since it happened to be true, he said it anyway. "I'm not feeling well."

Snape took a step toward him, looming more menacingly than ever. "Then why are you sneaking around here instead of going to the infirmary the way sick students are supposed to?"

"I'm not sneaking!" Harry said indignantly. "This is the shortest way to Gryffindor tower. And I don't need to go to the infirmary. I just need to lie down for a bit. Professor McGonagall said it was okay." Well, she didn't really, but he had asked Ron to tell her where he'd gone, and surely she wouldn't mind him having a quick lie-down, would she?

Snape glared at him for a while longer, black eyes glittering in his sallow face. Harry felt as if those eyes were trying to drill right into his skull and search out every little secret he might have hidden. He returned the glare as best he could, and eventually Snape gathered his cloak more tightly around himself and stepped back.

"Very well," he said in a tone that reminded Harry unpleasantly of Draco Malfoy's sarcastic drawl. "I shall walk you to Gryffindor tower. After all, we wouldn't want you to grow disoriented and wander off in the wrong direction, ill as you are."

"That's not necessary," Harry protested, but it was no good. Snape had obviously decided that Harry was up to something, and was determined to stop whatever it was. Harry didn't dare to argue too long. Snape was perfectly capable of taking points from Gryffindor even though the term hadn't officially started yet. In fact, he was probably counting on Harry to lose his temper and give him an excuse. Well, he was going to be disappointed. Harry spun on his heels and walked off down the corridor, Snape trailing just behind him. Harry resolutely ignored him, which actually wasn't very difficult, since Snape made no noise at all as he walked. The only sign of his presence was his huge, inky shadow gliding bat-like along the wall.

They reached the entrance to Gryffindor tower without incident. "Fiddle-dee-dee," Harry muttered, and the Fat Lady slid aside to let him enter.

"You look tired, dear," she told him as he brushed past her. Harry didn't bother replying.

He staggered up the stairs to the Fifth-year dormitory. His trunk was already next to his bed, Hedwig's cage perched on top of it. The owl gave a soft, concerned hoot as Harry sat down on the bed and began to untie his shoes.

"Don't you start," Harry told her. Hedwig blinked at him, silent. "That's better." He tossed his shoes under the bed and lay down. He was asleep in seconds.