Professor Snape in Muggle clothing was strange not for the usual wizard reasons, but because he actually looked normal, for him. Instead of black robes, he wore a long black coat with lots of buttons and looked, basically, exactly the same as he always did - like he got no sun, took no care of his appearance, and hated you personally. Harry felt very conspicuous trailing after him in his sweatshirt and baggy jeans, invisible broom in one hand and bag over the other shoulder. It turned out there was an apparition point in Little Whinging, but it was a walk from there to Number 4. He just couldn't visualize Professor Snape and his aunt and uncle in the same room. It didn't fit, in his head, they were two different worlds and the collision was giving him a preparatory headache.
"I can go on my own," he assayed.
"No."
"What are you going to say, though? They don't really... like magic. You might not want to-"
"Potter."
Harry paused, and watched Professor Snape weigh what he was going to say.
"I understand being ashamed of one's relatives. My father."
Professor Snape seemed to run into a wall, then, as if even saying the word father was too much for him. Harry watched him warily.
"In any case, I have met Petunia before. We will simply be... catching up."
Harry wondered a little wildly if he could get away with stunning his professor and running. Probably not, he thought morosely.
Professor Snape knocked on his aunt's door. His aunt opened the door, and paused.
"Mrs. Dursley," Snape said evenly. "May I come in? I've brought Harry Potter."
"We don't want your sort here. You're not welcome," she snapped, hovering in the doorway with glittering eyes.
"As one of Mister Potter's professors, I have a number of concerns to discuss with you," he said, coming inside quite as if she hadn't spoken. "We should sit down."
Aunt Petunia's eyes focused on Harry.
"Well? Make the tea," she snapped at him, quite as if he'd never left. Harry rolled his eyes and put his bag down, tucking his carefully invisible broomstick into the corner where no one would trip over it. (He was more worried about the broomstick than his relatives, in that situation.)
Harry busied himself making tea, trying frantically to eavesdrop on the conversation in the living room with no success. By the time he'd gotten in there, the pleasantries seemed to be over.
"I don't see how it's your concern how I raise my nephew," Aunt Petunia was saying hotly. "I've done as best as I know how, and he doesn't want much looking after."
"He is fourteen, and still requires some modicum of adult supervision. Surely you noticed he was no longer under your roof?"
"I thought he was sulking."
"I see," Professor Snape said silkily.
"Why're you the one coming around asking questions, then? Lily told me about you."
Harry turned to look at his professor, who had gone rather still.
"She said you'd gone quite wrong," his aunt continued with relish. "Started stalking her and everything, joined a gang, to tell her if you ever came around so she could tell you to knock it off. I was certain you'd end up in prison."
"My criminal record is not the topic of discussion today, Petunia. Nor is Lily."
"Why else would you take an interest in the boy?"
"You cannot imagine why someone would take an interest in Harry?"
"I've always said he'd come to a bad end, just like his parents."
A teapot on the mantelpiece exploded.
"I'll just... clean that up...." Harry said weakly.
"Reparo," Snape said, with a flick of his wand, and the teapot reassembled itself and levitated back to the mantleplace.
Aunt Petunia fainted.
"Erm." Harry patted her hand, and once she'd swum back to consciousness, handed her a cup of tea, which she clutched. "Where's Uncle Vernon, Aunt Petunia?"
"At work." She glared tearfully at Snape over her teacup. "He said your sort weren't allowed to come here, in his letter."
"Ah, but that depends on Harry living here and calling this place home, for some reasonable portion of the year. So try to notice him wandering off, and you'll never have to see me again."
"Good," she said viciously.
Professor Snape took a sip of tea.
"Jealousy," he observed, "Is very ugly."
"Me, jealous? What would you know about it, then? Or were you talking about yourself, Sevvy?"
"Merlin, I'd forgotten that particular unfortunate nickname. Professor Snape, if you please, Mrs. Dursley."
"Was there anything else, Professor Snape? Did you want to harass my son, next?"
She shot a nervous look upstairs, as if worried this would give Snape ideas.
"You knew my mum?" Harry interrupted.
"We were friends, as children," Snape said distantly.
"Best friends," Petunia added. "Always going on about how wonderful it would be once you could go away and leave all the rest of us behind, weren't you, Professor."
Harry considered this for a few seconds, not even sure where to start. Professor Snape's face as he said 'my father.' His mother's stalker? Joined a gang? That must be the Death Eaters, but... but....
"I cannot claim to have missed you overly much," Professor Snape said, dead dry. "The tea is very nice, thank you, Harry."
Harry was going to die of confusion and misery and go to the happy place in the sky with his parents.
"I'll put a leash on him. Happy?"
"Ecstatic." Professor Snape finished his last sip of tea and set the cup down. "I will see you when term begins, Mister Potter."
"...bye, professor."