Disclaimer: Sirius and James and any reference to the Potter-verse are JK's, or WB's or whoever else is getting a slice of the Harry Potter Pie. The Tenth Doctor (used here for the visual enhancements of the story), Torchwood, and his universe(s) belong to the BBC, and thus, to the Empire. Do not mess with the Empire. Not getting any money out of this, it's all done for the sheer joy of entertainment. Anything you don't recognise from either these universes is mine. Enjoy.

Part One: What?!

It started off as a regular day, all things considered.

The Sun was shining out his mass of rays, product of the ongoing atom-smashing it engaged in, as it would for another five billion years, give or take a millennium or two.

People were going about their respective businesses all over the tiny globe flitting across the universe at a thousand miles per hour, more commonly known as Earth. Shops opened on one side of the Earth while they closed on another. The wars that had been raging on in certain areas of the planet raged on as usual. Cars flooded the streets and motorways of all five continents. In Copenhagen, people cycled. The Sea Shepherds faced down whalers in the Arctic Ocean; Greenpeace was organising simultaneous direct actions (whatever that meant) in seven countries and having trouble synchronising their watches in all those time zones. Kids went to school. Grown-ups went to work. The homeless begged for money. Over half the population was watching the telly. A further quarter of it was online, downloading and chatting and web-surfing to their heart's content. The L.I.N.D.A. bunch especially. A new species of bacteria was discovered, at the same time ten animal species that were never even known became extinct. Some went to their churches to pay homage to their gods. The ill were ill. The rich enjoyed their riches. The industries were industrious...

In short, some died, some lived. The rest teetered in between both extremes, with varying degrees of success. The dolphins were debating leaving the planet early and trying come up with a way to thank the humans for all the fish they had been given.

Even the Doctor was going about his business. Which, today, happened to be Earth-based. And which, at the moment, was roughly centred on running like the Dickens.

His splashing footsteps, which echoed in the tunnel he was trying to escape from and which in turn was located way, way below London, were not the only sound heard down there. Nor were his ears the only ones hearing it. Dozens of heavy steps echoed and splashed after him, making the ground shake. They weren't the only thing sent after the doctor, either; there were voices, ordering him to stop already and give in to his inevitable fate; there were bullets accompanying these voices, trying to enforce the statements that reached his ears.

Of course, the Doctor responded by just running faster. Having two hearts was handy in many ways. A greater endurance than most was just one of the many perks of being a Time-lord.

Even if he was completely lost and had no idea where he was going.

Wouldn't be the first time.

The Sontaran troops hot in pursuit, though, seemed to have a pretty good idea of where he was headed; they proved his theory right when, after turning a sharp right corner, another dozen Sontarans cut him off up ahead. The Doctor backpedalled. The Sontarans behind him shouted in anticipated victory. The Doctor took a left, then a right, another left...

"I swear I saw a ladder here somewhere," he muttered, stumbling over his feet and nearly falling on his face in the muck that coated the inside of this old, disused sewage system. It was, perhaps, a good thing: a handful of bullets narrowly missed his head and impacted the walls of the tunnel all around him. "OY!" he shouted at the Sontarans. "Watch it! You'll hurt someone at this rate – me!"

They were annoyed, certainly. But, as the Doctor believed, this wasn't a reason to shoot him like he was the last turkey for Christmas. Having ruined their plan of blowing up the Houses of Parliament while it was in full session, though... could be seen as an offence punishable by death in their book. He still carried the detonator with him, as he had been found out before he could permanently disable it.

A good thing, too. The thing would have blown up had he tried to disable it then; and he needed two things he didn't have in order to make it safe – time, and his TARDIS.

Of course, the Sontarans knew this, hence all the shooting. They didn't care who died in the explosion that would wipe out half of the City of London, after all, as long as many did so, leaving them a free run of the government amidst the ensuing chaos. Talk about a coup d'état. If they managed to kill him, well. That was exactly what would happen. There were thirty-six explosive devices still attached all over the building, all controlled by the small black device rattling about in the Doctor's long coat, all of them still active.

He turned a left corner, backtracked in a hurry as he saw the Commander of the Sontarans – the one with the huge gap between his front teeth – leading what looked like an entire battalion down another bit of the sewers a little ways ahead.

Some fix, this. The Doctor was panting, feeling increasingly cornered. He rarely lost his way, but as it happened, this was one of these rare times. He hoped the Sontarans were as lost as he was. Maybe he should hide the detonator and hope for the best?

He was pondering this most weighty decision – after all, the Sontaran commander would want the honour of pushing the big red button of the detonator himself. If he hid it, then he could perhaps hope to stay alive enough to negotiate his way out of these tunnels and get a chance at stopping them—

No sooner had this thought crossed his mind, that a bullet hit him in the leg. With a scream, the Doctor went crashing down, hard, into the muck—

He was unaware of the fact that the Sontaran army wasn't the only one following him. There were two sets of footsteps hurrying around these tunnels that were different; and these two, at least, knew where they were going.

Sort of.

Then again, the Doctor was rather busy at the moment, trying to get up past the searing pain in his leg, which had just decided it wasn't going to play along anymore, thanks – and staring at the approaching Sontarans. They were aiming their guns at him. He hated guns with a passion. Interesting, really, how no matter which corner of space life evolved, eventually every single one of them developed a distance killing device. i.e., a gun of some sort or other.

They weren't shooting, though, he noted, clutching his leg and trying not to pass out right there. Not yet, anyway.

Which could only mean one thing.

And it was a very bad thing, too; the commander was worse than the lot of them put together.

The Doctor started searching his pockets for his sonic screwdriver, maybe if they waited long enough – a few seconds at most – he could reverse the mechanism of their guns and render them useless.

He nearly cried out in frustration. His sonic screwdriver was...

"Gone!" he wheezed, wiping at his sweaty face with a mucky sleeve. Wincing at the movement, he clutched his leg with one hand as he felt around for it; maybe it had only just slipped out of his pocket?

"Ah, the brave Doctor. Not so cocky now, are we? Not so brave, at any rate, cowering like a kicked mongrel," The Sontaran commander leered upon arrival, even as his men – could they even be called that? – stood aside to let him through.

"I'd be standing up if you hadn't shot me in the leg!" the Doctor snapped back. "Well, then again, I'd still be running if you hadn't shot me, so you might have a point."

"You have something of ours, Doctor, and I know you still have it in your pocket. Hand it over, and perhaps we shall let you watch your precious Earth die before you follow her fate."

"I don't know what you're talking about," the Doctor replied through gritted teeth. Already he was regenerating; the bullet lodged in his thigh was slowly, but surely, on its way out... If he could only get enough time to regenerate, then maybe, only maybe... he could make another break for it. Of course, he'd have to get past some thirty feet of solid concrete, but—

"No? A pity. In that case, there is no reason whatsoever to keep you." The Sontarans cocked their guns at him. "What are your last words then, Doctor?"

"There are several very good reasons why I wouldn't recommend shooting me right now," the Doctor started. He was already seeing black specks. Would this be his death? It didn't feel right for a death... "One—"

He didn't get any further.

"Fire!"

Already the Sontarans were shooting. As if in slow motion, he could see the flames issuing forth from the barrels, could almost follow the lightning-fast, spiralling patterns the bullets cut through the air—

Only to watch them freeze right before impact.

And fall to the ground with a wet, muffled clatter.

"What?!" the Doctor muttered, staring at the hail of bullets falling to the ground without hitting him, even as the Sontarans' cries of confused rage were heard. A ruckus seemed to have started at the far end of the tunnel as well, which was followed by crashing sounds of – was that a snigger right next to him? – Sontarans hitting the ground.

"It can't be..."

"Oh, yes it can," a voice said confidently, coming from right next to him. The Doctor turned around so fast he cricked his neck... but there was nobody there!

"What? What?!" asked the Doctor, baffled, even as a hand closed around his wrist and pulled him away from the Sontaran commander's massive fist, which in turn connected with the wall, rather than his face, which it had been aiming for.

"What is this treachery?" the commander roared. "Show yourselves, cowards! Face your enemy!"

A bark of a laugh was his response, even as the front-most row of Sontarans went crashing, face-forward, to the ground. The Doctor's jaw dropped in sync with them.

There, in front of him, stood a black-haired boy, wielding what looked like a metal-studded club and grinning at the Sontaran commander as he picked his way along the body-strewn tunnel.

"What did I tell you, James? It's exactly like on the telly! One whack to the little tube on the back of their heads, and they're out of commission," the kid grinned at the Doctor, wiggling his eyebrows at him. "Hello there."

"What?" said the Doctor again.

"Do the last one then, and let's get out of here – I hope you remember the way, I'm totally lost," said the disembodied voice from before. It too, sounded like a boy's voice.

"What?" the Doctor was very confused. His leg was twinging up a storm as well. That never helped; also, he was rather lost as to what was going on... And that, in itself, was rare.

So was the Sontaran commander, although that wasn't uncommon.

He had been aiming his gun at the Doctor when the disturbance started, but was now staring, gob-smacked, at the kid climbing over the bodies of his fallen soldiers like it was an everyday occurrence. He rubbed his small, beady eyes, but the kid was still there, the eerie glow of some unnamed light source giving him an added air of ghostliness.

His confusion gave way to rage in the space of a blinking, however, and not a second later he was calling for reinforcements through his intercom. And charging the boy with the club with the Sontaran Battle Cry of Raging Fury.

"RAAAA!" roared the commander, lunging for the boy before the Doctor could so much as react. Which, luckily, wasn't necessary.

The Doctor's eyes widened so much they were threatening to pop out of their sockets: The boy – it was a boy, wasn't it, he couldn't possibly be older than fifteen – sidestepped the commander, flourishing a hand at him as if to let him pass – and the commander went down face forward, only to get a whack to the back of his head with the club.

"There," said the boy. "I hope you're happy for ruining my fun, Prongs." He had turned back to face the Doctor, who was soundlessly opening and closing his mouth. "Hello," the boy repeated, tossing a thin metal rod at him. "You dropped this back there – what does it do, exactly?" he added, as the Doctor caught his sonic screwdriver. "I kept twiddling it, but nothing happened. Except for a weird, dog-awful noise and a blue light. Is it a torch? Or, maybe it's broken?"

"What?"

"Not one for conversation, this one," the disembodied voice commented, making the boy snort.

"Who's there?" the Doctor managed, but he went largely ignored.

"He's just surprised, leave him alone. And take that cloak off; he'll think he's going bonkers if you carry on like that."

"Spoilsport," the voice muttered, but seemed to comply, as the next moment, there was another black-haired boy standing there, holding a silvery something in his hands and grinning at the Doctor. This one had very untidy hair and glasses, and was dressed in much the same fashion the other was; jeans, a black t-shirt, and a long black coat. He extended the hand that wasn't holding the silvery fabric towards the Doctor.

"Hullo," he said, "I'm James Potter. This is Sirius Black. He knows the way out."

"What."

The boys exchanged a look that was part amused, part concerned.

"Can you walk, at all?" asked Sirius, the boy with the club, crouching next to the Doctor and examining him closely. His eyes were an eerie, almost unnaturally clear grey, shining off-white in the flickering half-light of the tunnel. "They hit him on the head, you reckon?" That last was directed to the other one.

"Nah, I didn't let a single bullet through," James replied, sounding rather pleased with himself. "They did get him on the leg, though, but that was before I could get here. I don't think he'll be able to walk. Say, Sirius. What are those things called, then? I'm pretty sure you said they weren't trolls, and up close, well... They don't look like trolls."

"They're the baked potato regiment, what do I know," Sirius answered off-handedly, still peering at the Doctor and making James chuckle. "He does look rather shocked, and if he's hurt, we won't get much help out of him. The fact he was nearly executed probably isn't helping either... Give us a hand, there's a good man." He hooked one of the Doctor's arms around his neck and hoisted him up. "Way out is over here, and we'd better peg it – there's more jacket potatoes coming. We have about... five minutes."

"I'll take your word for it," James answered, helping haul the stunned Doctor down the tunnel after spotting the injury in his leg and bandaging it in a blinking. The Doctor watched them mutely, trying to make sense of things. If there was one thing he couldn't handle, it was not understanding something. And this, he decided, was far out.

Kids simply didn't show up in old, abandoned sewers. Or do any of the things these two were doing.

His speech seemed to want to figure this riddle out as much as he did, though, because he opened his mouth, and out came not 'what?', but, "Who are you, then?"

"We told you. Sirius and James."

"What are you doing here?"

"What does it look like?" James asked back, snorting. "You looked like you could use some help, what with those armoured trolls hot after you and everything..."

"We like tunnels," Sirius added. "And, dunno, we thought it was unfair for you to put up with that lot on your own. We also found them leaving these all over the place." He pulled a few round disks out of one of his coat pockets, showing them to the Doctor. "These were all over the Parliament, the potato bunch was sticking them to the walls. We figured that wasn't exactly a good thing, so we brought them along. I think we managed to get them all. They're flashing and things... Say, what do they do?"

At last, something he understood!

"They're bombs... Explosive charges, with a wireless, long-distance detonator," the Doctor said at once, taking one of them. Now he had a chance to take a breath and realise he was, in fact, not dead, he was also regaining his usual quick articulation skills... And it was the boys' turn to look nonplussed.

"You mean, these.. actually blow up?" Sirius asked slowly, his eyebrows rising in earnest surprise.

"But they're tiny," James cut in, "can't do much damage with that, can you?"

"You could blow the entire city to bits with these," the Doctor answered, much to the boys' undisguised amazement. "How did you take them off without setting them off? They're rather fragile."

"Er. We just... took them," James shrugged. Then he chuckled, turning to Sirius. "Mate, you were whacking away at the potato heads with your pockets full of bombs. Fragile bombs, at that." They both seemed to find that very funny for some reason. The Doctor watched them for a few moments, earnestly amazed. Humans were so surprising sometimes.

"Brilliant," Sirius agreed, chortling and bouncing the things up and down in his hand, completely ignoring the Doctor's instinctive flinching. "This way here, then." He led them, still half carrying the Doctor along, to a tunnel that sported a vertical shaft, from which a sliver of light issued. "I'll go first, and we'll just levitate him up, alright?"

"Don't blow anything up," James reminded him. Sirius snorted and started to climb up.

"Yes, mummy."

"Maybe you ought to sit down for a bit," James told the Doctor. "He's gone to check if the coast is clear."

"I think I can manage," the Doctor cut in. "It's best if we all go up. Sontarans don't fit in narrow spaces very well... come on."

"But I saw you get shot," James told him, pointing at his leg. "Wait until Sirius gives us the all-clear and we'll get you up in a second. No need to strain yourself." The Doctor flashed him a smile.

"I'm doing better now." To demonstrate, he stood on his feet, which held his weight, even if his injured leg was still painful as anything. "See?"

James let out a low whistle.

"Oy, Sirius!" he shouted excitedly up the shaft, making the Doctor cringe. "You were right! It's just like you said – he's all healed up!"

"I'm always right," came the answer from high above them. "And now that you've drawn attention to where you are, I suggest you get up here, pronto."

"Oh. Right. Sorry about that."

"Yeah, you sound really remorseful there, Prongs."

James snickered, giving the Doctor a helpless shrug.

"Get cracking, the taters are almost where you are," Sirius' tone contained the exact amount of urgency needed to get James moving, who nodded the Doctor towards the ladder.

"You heard him, go on."

"How does he know?" asked the Doctor, climbing up the first few rungs. "How does he know where they are?"

"He can smell them a mile away," James said matter-of-factly. "Says they remind him of... pork chops gone bad."

"Ugh. Can't be pleasant." The Doctor climbed up a little higher, James following suit. The distant cries of their pursuers could already be heard faintly, splashing their way towards them.

"Yeah. He sniffed you out too. Said you smelled like vanilla ice cream, but personally, I think he was just taking the piss."

"Get a move on, you'll hear them in a sec," Sirius called down. "That means they'll be right where you are—and there's enough room for them to go after you."

"I think they won't be able to," the Doctor said, setting the sonic screwdriver and handing it to James, who was a little ways below. "Hold it against the rungs, hurry."

"What's this do, then?" Of all the times to demand an explanation.

"Just— do it!"

"Alright, alright..." Rolling his eyes, James touched the screwdriver to the rung he'd just left, watching as it burned a hole through the metal. "Oh, that's neat," he commented, apparently unbothered by the fact more Sontarans had spotted them and were running their way with the force of as many charging rhinos. "This here though, is loads faster." He returned the screwdriver, pulling out a stick – the Doctor was about to ask what that was all about, but one tap of the stick later, the lower end of the ladder was crashing down already.

"Oy, stop gawping and start climbing," Sirius reminded the Doctor some ten feet higher up. "We're nearly at the Tube, we can lose them there!"

Reluctantly and full of questions dying to burst out, the Doctor obeyed; this meant he completely missed the diversion James left the Sontarans, in the form of a metal dragon he'd charmed out of the broken-off ladder, and which did a terrific job at turning the tables on them in less than a minute. Instead, he climbed out of the shaft, aided out by Sirius, and trotted with them both out of the network of service tunnels and into Westminster Station.

This day was far from ordinary already, and it wasn't even lunchtime.

TBC. R&R and all that.