Title: The Lost Boy
Format & Word Count: Fic, 2,120 words
Rating: PG
Fandom: Harry Potter, Doctor Who
Warnings: DH spoilers, though if you've already read the name of the characters in it, that's basically the only spoiler.
Summary: Out Christmas shopping with Harry, five-year-old Teddy gets lost in Knockturn Alley, and an unexpected rescuer turns up to help him out.
Author's Note: Takes place between the actual end of DH and the epilogue, and sometime between seasons 3 and 4 of Doctor Who. See, I'm planning this epic crossover in the same verse as Too Close to the Moon and A Movement of Darkness on Darkness, which also happens to be my way of straightening out my personal canon in regard to Certain Character Deaths at the end of DH. This little bit of was just going to be a memory of Teddy's, when he meets the Doctor several years later and realizes he's seen him before, and then I figured, well, it works as a short stand-alone. And yeah, the title is mostly 'cause...I couldn't think of anything else and figured it was a good crossover connection, even if "The Lost Boy" was a Sarah Jane Adventures episode and not a Doctor Who one.

The Lost Boy

He is five years old and Uncle Harry's taken him to Diagon Alley for Christmas shopping. Uncle Harry's told him not to wander off, and so did Granny before they left the house, and he's trying to be very good so he'll get a miniature broom this year, but there's too much to see—snowmen enchanted not to melt, carolers, glittering lights everywhere, a perpetual snowfall over much of the alley that never piles up on the cobblestones. Uncle Harry seems just as distracted, and when they reach Swept Away, the newest broom shop, he stops, gazing in the window. "Look at that, Teddy—Firebolt's got a brand-new version out, and I didn't think they could get any prettier…"

"Is it fast?" Teddy asks.

"Oh yeah," Uncle Harry says, still staring raptly. "Leave your stomach behind if it wasn't so smooth." He taps one finger against his chin. "Maybe...if I call it a Christmas present to myself…"

Teddy looks at the broom a moment longer, but apparently he isn't seeing it the same way Uncle Harry is, because it just doesn't look that special to him. Figuring it's another one of those things he'll understand when he grows up, he wanders to the shopwindow next door, grinning when the kneazle plushie in the display waves at him. Teddy waves back.

Uncle Harry's cloak flicks past the corner of Teddy's vision, its owner taking off at a brisk stride down the street. Teddy hurries to catch up with him, struggling to keep his eyes on the cloak as he dodges between other legs and boots and cloaks on the busy street. He's focusing so much on keeping up that he doesn't realize he's following the wrong person until the cloak makes a quick right turn into a dimly lit shop and Teddy sees the grey hair above its hood. He stumbles to a stop, staring. It hasn't occurred to him before that most adults look the same from the knees down.

Teddy turns around, thinking that he can't have gone far and then that he has no idea how far he followed the man in the cloak that looked so much like Uncle Harry's, and sees a faded, cracked sign hanging above an abandoned shopfront: Borgin & Burkes. He knows the name—Uncle Harry talked about it at dinner once, not too long ago. "We just closed it down for good, but that'll just drive most of their business underground; Knockturn Alley's still a pretty dodgy place," he said, almost continuing into something about the black market and what sounded like body parts before Aunt Ginny shushed him with a look in Teddy's direction. Why she seemed to think it so important that Teddy didn't hear more, he didn't know, especially since he'd already heard more than enough from Granny to want to stay far away from the place.

He looks around wildly. Bad enough that he's already got himself lost, but he shouldn't be here, definitely shouldn't be here—he backs up, turning, and bumps into a hag, who grabs his shoulder as if to steady him. She smiles down at him, and Teddy shrinks back, his heart beating very fast, reminded suddenly and unreasonably of a graveyard. Her teeth do look a bit like headstones.

"What's a pretty little bit like you doing here, pet?" she asks, her hand gripping his shoulder just hard enough to hurt. "Little boys shouldn't wander away from their mummies. They might get hurt. You wouldn't want that, would you?"

"I didn't," Teddy says. "I mean, I haven't got a mum. I was here with Uncle Harry and I got lost and—"

"Uncle Harry?" she says, her fingers tightening and eyes gleaming in a way Teddy doesn't like. "Harry Potter? You're a finer catch than I thought, sweets. The werewolf's cub himself, eh?"

"Let go!" Teddy cries, trying to pull away. She seizes his wrist, sharp nails digging into his skin.

"You look like him, only without the scars." She draws the back of one finger down the side of his jaw, then turns it, letting the sharp point of her nail scratch his skin.

"Well now, what's this?"

The hag lets go abruptly, and Teddy stumbles back, blundering into a bony leg in pinstriped trousers. He looks up: it belongs to a spiky-haired man in clothes slightly too odd to mark him as a Muggle, his long brown coat—not a robe or a cloak—hanging to his ankles.

"Just having a chat with the young master here, not that it's your business," the hag says, reaching for her wand.

"Oh yeah, that's me, always meddling in other people's business," the stranger says. "Keeps things interesting." He glances down at Teddy. "What d'you say, though, should I make it my business?"

Teddy sniffs and nods, latching onto the stranger's trouser leg. "I thought I was following Uncle Harry, only it wasn't him, and I don't even know how I got out of Diagon Alley, and—and there's scary people here!"

"Scary people in Knockturn Alley? Tell me something I don't know," the stranger says, but his eyes are kind.

"I didn't want to come here, I got lost—I didn't mean to—"

"Nah, 'course you didn't," the stranger says, twitching his trench coat open so it drapes over Teddy, half hiding him. "My friends are always wandering off and getting in trouble, and they're way older than you. Rule number one, don't wander off, I've got to start telling them that…"

The witch snarls, pointing her wand at the stranger's chest. "Shut your gob, leave me the boy, and I'll let you keep your skin. I found him first."

The stranger stares her down, hands in his pockets, clearly unimpressed. "Finders keepers, hm? You're planning to, what, keep him for ransom? Sell his blood on the black market? Something even nastier? Actually, don't tell me, I don't want to know. But come on, d'you really think the Boy Who Saved the World will let some random hag get away with kidnapping his godson? Plus you don't want to hack off Andromeda, I'm told. Right nasty in a pinch."

"Stupefy!" the hag shrieks.

The stranger dodges the spell with surprising speed, shoving Teddy aside behind a pile of crates. "All right then, since you're here, I've been wanting to try a little experiment—"

"Confringo!"

The stranger ducks the hex again and pulls a short metal wand from his trench coat. "Teddy, what d'you suppose would happen if, hypothetically, someone hit a wand with a sonic device tuned to the exact right frequency?"

Teddy blinks at him. "Um…"

"Yeah, me either." The stranger points the metal wand at the hag, its tip flaring blue, and a high-pitched buzzing tickles Teddy's ears as the hag shouts another curse—

—and the hag's wand explodes with a shriek. She stares at her hand, dumbfounded. "What—how did you—"

"Ah, but that would be telling," the stranger says, and he isn't grinning anymore. "Now let me tell you this: there are a number of people who would dearly love to toss you in Azkaban just for thinking about hurting this boy—and considering they all helped kill Voldemort, they could do it." The hag flinches, and the stranger's eyes darken with disgust. "Five years gone and he's still got people like you afraid of his name. Don't any of you have an iota of pride? Get out of here before I call in some Aurors."

The hag flees, cloak flapping behind her. The stranger raises an eyebrow at a couple of transfixed onlookers, who quickly turn away, and then offers a hand to Teddy. "Let's get you back to your Uncle Harry before he has a panic attack, shall we?"

Teddy lets the stranger help him up and doesn't let go of his hand. "Who are you?"

"Oh yeah, never properly introduced myself, did I?" the stranger says, leading Teddy down a narrow offshoot of Knockturn Alley. "I'm the Doctor."

Teddy frowns. "That's what Muggles call their Healers. Aunt Hermione said so."

"Hm? Oh, not that kind of doctor. Just…the Doctor. And I just don't like that term, 'Muggle'…I know all you lot don't mean anything by it—well, most of you anyway—but dividing the entire world straight down the middle, magical or Muggle, I mean that kind of strictly dichotomous thinking is so limiting, especially when there's so much more out there that most of you don't even dream of. People think about time like that too, sort of, but from a nonlinear, nonsubjective—"

Teddy decides not to try understanding any of this. "So you're not a Muggle?"

The Doctor sighs. "Just when I was getting warmed up. In your terms, yes, technically I suppose I'm a Muggle."

"But you had a wand—"

"Oh, this?" The Doctor pulls the wand from his jacket again and tosses it up in the air. "Sonic screwdriver. Not quite as versatile as a wand, I'm afraid, but dead useful all the same." He pockets it before Teddy can ask more. "Here we are then, Diagon Alley!"

Teddy grips the Doctor's hand harder with a sudden rush of panic. "But I don't know where he is, what if I can't find him—I don't want to be alone!"

"No," the Doctor says, crouching and putting one hand on Teddy's shoulder, his voice suddenly quiet. "No, I imagine not. I'm going to help you find him, Teddy, all right? You won't have to be alone."

There's something in his voice that Teddy doesn't understand, and he looks up in time to catch the Doctor's gaze—which isn't hard, now that he's on Teddy's level instead of several times taller. The depth of sadness there nearly knocks Teddy over. The Doctor's dark eyes seem to go on forever and ever, like he holds the whole universe just behind his vision, the universe and an eternity of loss—

The Doctor blinks and straightens up, shaking his head a little as if realizing he's let Teddy see something he hadn't meant to. "See anybody you know?"

"No," Teddy says, still feeling a bit dazed. Without realizing he's going to say it, he adds, "You haven't got anyone waiting for you. You're all alone."

"Better that way, trust me," the Doctor says, not looking at him. "Lousy track record."

"No," Teddy insists, and he might still be lost with only a strange man he doesn't understand at all for company, but he does know this much. "Uncle Harry says you can't do anything on your own. He said he couldn't beat Voldemort without his friends."

"Well, yeah," the Doctor says. "Hard to save the world by yourself. But people I—" He stops, shakes his head. "Look, the point is, you're not alone. Remember that." He pulls out his sonic screwdriver again. "Now then, Teddy Lupin, allons-y, let's find your uncle, or godfather, or whatever exactly he really is—and I think, if I'm very lucky or possibly just very clever, and I'm often both…" He takes both of Teddy's hands, turns them palms up, and scans over the skin with his sonic screwdriver. "There we go, trace DNA, enough to track him down—or maybe enough for a cloning even, with a really good laboratory and enough motivation, although personally I think one Harry Potter is plenty, don't you?"

"Yes?" Teddy guesses.

The Doctor scans the street with his sonic screwdriver, and it starts beeping as he points it down toward Weasleys' Wizard Wheezes. Teddy sees him first: Harry's standing outside the shop with George, looking upset and gesturing wildly; George has his hands up, palms out, as if trying to calm Harry down—which, Teddy thinks, is not a very George-like thing to do.

"Go on, then," the Doctor says, letting go of Teddy's hand and giving him a gentle nudge. "Go put The Boy Who Blames Himself for Everything out of his misery."

Teddy takes off running and doesn't stop until he collides with Uncle Harry's shins, wrapping his arms around Harry's leg and only letting go when Harry drops to his knees and hugs him.

"I wasn't looking," Uncle Harry's saying, "I got distracted and thought you were following me and—where did you go?"

"I got lost," Teddy says against Harry's cloak, feeling sniffly again now that he knows he's safe, "Knockturn Alley—a hag wanted to take me away—"

Harry goes pale. "But you're all right? No one hurt you?"

Teddy shook his head. "A man helped me," he says, realizing he never said thank you. "He's right here—"

But when he turns to look back, the Doctor's already gone.