The skies of London at this time have not yet been choked by the smoke and soot of a later age. The factories and mills that will churn out the airborne filth have not yet been built. But the city still has a distinctive smell of its own. People who imagine time travelling often forget that the past is not just a picture out of a history book – it is a living, breathing place, filled with plants and animals and people, and all the baggage that comes with that – the sound of people in the distance, talking and arguing; the smell of pre-industrial life, a time before plumbing, when the street gutters channelled more than rain. Even the river gave off its own smell, though not an unpleasant one – no sewers ran into it yet. In Eastcheap, a thin cloud of smoke rises from the ruins of what used to be the Merlin's Beard pub. By some miracle, despite every building around it being made of wood with straw thatch roofs, the fire had stubbornly refused to spread. A few city watchmen had coerced and bullied the small crowd that had lingered into a reluctant bucket chain to douse the few smouldering embers.

The people who live here are used to these smells, though a human time traveller from the future, a time of indoor plumbing and internal combustion exhaust, would have a hard time coping with the smell. The Doctor kept a few pegs in one of his cavernous pockets for just such a purpose, but he never used them himself. Countless worlds throughout the whole of time would desensitize anybody, and the Doctor preferred to experience everything – it reminded him that these were real places, with real people and real histories. It was too easy to lose track of the fact.

Nevertheless, he was sorely tempted to reach for a peg as he coughed, ducking down below the layer of tobacco smoke carpeting the ceiling of the tavern. The air was thick with the smell of beers, wines and ales, breads, smoked meats and the people consuming them. Will grinned.

"You fare better than most first-time visitors to Lincoln's Inn. It takes its toll, does it not?"

The Doctor grimaced. "It'll…linger. Can we just sit down here?"

"I thought we could get a booth, Doctor. A little…privacy."

Apprehensively, the Doctor followed Shakespeare as they wove through the motley crowd that filled Lincoln's Inn; sailors, bricklayers, merchants and prostitutes, all talking, laughing, arguing and cheering as a small band of actors played out a pithy scene in the tavern courtyard. Up a set of stairs, onto a balcony seat, and the Doctor could finally clear his lungs, giving a final hacking cough as the two took a seat.

"I keep forgetting this is when tobacco starts getting popular," he said, by way of an explanation. "You should stay off it," he added. "It's bad for your health."

Shakespeare shrugged. "I keep to the opium myself. The usual, Nancy."

This last statement was to a serving girl who had approached the table behind the Doctor, who smiled and gave a curtsy, adding a sly wink to the Doctor, who returned it with a look of bemused incomprehension. He looked at Will, who chuckled.

"You have no eye for the ladies, Doctor?"

"Flirting later, Will. Now, what do you know about that thing?"

The smile faded quickly as Will's brows furrowed. "The demon that escaped? Nothing."

The Doctor raised a curious eyebrow. "Nothing else unusual happening lately? No ghosts or monsters or vampires or lights in the sky? This just came out of the blue?"

"As far as I know, yes, Doctor."

"Okay. So, get a timeframe. How long has it been since we last met?"

"You mean since you ran from the Queen from my theatre? Six months. The crowds are still demanding a repeat performance!"

The Doctor smiled. "Ah, give 'em a flashy light show and a bit of excitement, and you've got 'em in the palm of your hand. That's what people really go to a theatre for – a spectacle!"

"We make do. The other companies believe it was a royal performance, and who are we to deny it? You can't believe how much money we're taking in!"

"Oh, I think I can. And it's winter, so…late 1600, 1601? I'd say it's still 1601. What was your last play?"

Shakespeare simply nodded down at the actors in the courtyard. Over the softened background of the tavern business, the Doctor could hear the strains of "To be, or not to be: that is the question."

"Ah. I always loved that one. So it's been…twelve months, blimey, how does time fly? And between then and now, nothing…odd has happened?"

Shakespeare shrugged. "We fight wars in Ireland, Spain is always perched on the point of invasion, plague occasionally sweeps through the city, and there are still rumours of plots against Her Majesty. But this is daily life. Of true oddities that you might concern yourself of, I know not."

"So this is out of the blue. Right. Okay then."

"Is that not a good thing?"

"Oh, well, yes, of course it is. I mean, on the one hand, nobody's been killed yet, and the only thing destroyed is one pub-"

"The Lubber's Head will not be mourned, especially not by its neighbours, Puritans the lot of 'em," Shakespeare interjected.

"But on the other hand, it means we don't know anything about what they want, why they're here, and what they'll do. It's very inconvenient."

Shakespeare snorted in amusement. "I'd forgotten the strange ways you worked in, Doctor. Now, if you have no more questions for the moment, then might I ask some of my own?"

The Doctor frowned to himself – and then shrugged. "Oh, what the heck. You're in this far, might as well go all the way."

"I'll hold you to that, Doctor," Will said, winking. "Are you alone in London? Or is the good mistress Martha around here somewhere?"

The Doctor's face grew suddenly stony. "She…she went home."

"Why? The wonders of the worlds you must travel to, the times you could see-"

"Some things come at too high a cost," the Doctor said darkly. "And Martha paid for it."

"And you've been travelling alone?"

"Well…no, there was…somebody else."

Realising with a small amount of panic that this was a subject that he should not have broached, Shakespeare changed tack. "So what brings you to merry London town?"

The Doctor smiled wryly, appreciating the injected cheerfulness. "Well, I was just passing through the neighbourhood, and I thought, why not pay a visit?"

"You got lost, didn't you?"

"Yeah. I was aiming for Barcelona."

"Aim for Spain, land in England? Fortune smiles upon you."

The Doctor ignored the jibe. "Anything else you want to know?"

"For me, six months have passed. How long for you?"

"Three years," the Doctor said with an odd certainty. "'Round about. Give or take a few months. Or years. I have kind of a floating timeline, and honestly, you kind of lose track of dates between stopping the end of the worlds."

"For a Lord of Time, you seem unable to keep your dates in order. Your social calendar must be a mess."

"Well, I mean, it's not as if a calendar has any meaning any more," the Doctor said offhandedly. He paused. "Hang on, since when did you know I was a Time Lord?"

Shakespeare laughed. "Doctor, I'm a writer. I did my research! You are not as anonymous as you think yourself to be! Your stamp can be seen everywhere I look: Bosworth, Hastings, the Magna Carta, Greece, Rome, Venice-"

"Venice? I look forward to that one!"

"But in all my readings, I have never seen anything like these demons."

"Well, what's a Demon?" the Doctor said dismissively. "Just something scary you've never seen before! I've had plenty of people call me a demon. Do I look demonic to you?"

Shakespeare carefully neglected to mention the strange clothes, wide eyes, mad grin and the vague scent of smoke that still hung about them. "Not in the least."

"There you go then! Some people call them the Fungi of Yuggoth, though technically they don't come from Yuggoth so it's a bit of a misnomer. They call themselves the Mi-go – they're a fungal lifeform, very advanced, usually explorers and scientists. Not always the good kind, but they're not invaders. Which means that they have a problem, and that means we have a problem, one that we need to deal with quick."

"But…it set fire to a pub!"

"Yep! Fungal lifeform, remember? Compared to its own world, this city is a freezer. Can you blame it? At least nobody died, and with a bit of luck its patrons will reform and live happy, fruitful lives!"

"Or go down the street to the Pike's Head."

"Oh, you have to be such a cynic."

"But why are these…Yuggothians…here in the first place? If our world is intolerable to them, why come?"

"I don't think they had any choice," the Doctor replied, steepling his fingers. "It said there were cracks, that its world was consumed by fire...maybe the cracks led here, to London, 1599. Well, they're hardly the first refugees you've taken in, are they? You've got Jews, French Huguenots, even Africans all living here, setting up shop, and living their lives. London's full of refugees, maybe it just wanted somewhere it could fit in?"

Shakespeare gave the Doctor a long look. "I think," he said at last, "that I am going to need some help on this one."

The Doctor spread his arms wide and grinned. "Ta-dah!"

"A little more than that, I think." He sighed. "Her Majesty must, of course, be informed of events."

The Doctor grimaced. "Do we have to? I'm quite attached to my neck. I like my neck! I need my neck! And besides, what are you going to say? A demon set fire to a pub? You'll be laughed out of the palace!"

Shakespeare shrugged. "Ay, perhaps. And the thing did fly away after."

"Maybe we could track it down? It's hard to laugh at a demon when it's in front of you. And I really want to know more about these cracks, whatever they are."

"A thing that flies may leave no footprints, Doctor. Have you a means to track such a timorous beast?"

The Doctor reached into one of his cavernous pockets, rummaging around, his hand coming out holding a triangular machine that even to Shakespeare's inexpert eye seemed cobbled together from strange, disparate alien machines, with a blinking blue light. Despite the privacy the balcony seat afforded them, the Time Lord still kept it out of sight of the regular patrons, leaning forward to lower his voice – as though talking of demons and time travel was any less conspicuous.

"Well, I might."

Shakespeare grinned. "Always full of surprises, Doctor."

He hurriedly placed the device back in the pocket, an echoing "clunk" reverberating from the coat, as the girl walked over, carrying a wooden tray of mead. Will smiled, palmed a few coins into her hand, and said, "So, we have a plan then! We track this creature to its lair, drag it before the Queen, and hunt down the rest of its kind before they can do more damage. Well met!" he said, lifting his mead in a toast.

"Hunt, yes," said the Doctor. "Kill? No. They're just lost, and trapped here – it's not their fault they're stuck here! If they're planning something, I'll stop them. But I've seen too many species wiped out just because another thought it was attacking them. Most of the time, it's the human race doing the wiping out."

"Surely we have a right to defend ourselves?" asked Will. "If these were Spaniards, would you have the same-"

"Wait, hang on a sec, "We"?" asked the Doctor. "Since when did Will Shakespeare become the voice of the government?"

Will glowered, and then sighed. "You might as well be told, then. I-"

The Doctor held up a hand. "No, no, no. This isn't happening. Next thing we'll be setting off together, bonding, sharing witty repartee. I don't need another companion. I can do this myself. Thanks for the help, Will, but I can take it from here."

Will frowned. "Alone?"

"Oh yes. I'm going to find the Mi-go. I'm going to find these cracks, and I am going to sort them out once and for all. And you know what?"

"What, pray tell?"

"That serving girl hasn't moved an inch since she came over."

The two of them looked – the girl was, indeed, standing stock still next to their table, so still that they hadn't noticed her. Staring straight ahead. And with a pair of silver metal objects attached to her ears, blue lights blinking.

The Doctor's face fell. "Oh no. Not this again."

There was a commotion beneath them, people suddenly milling about confused, interrupting the play in the courtyard. And then somebody screamed, and the crowd went from milling to running. They heard a low growl, and a shaggy form leapt onto the middle of the courtyard, scattering people as they scrambled out of its way. It lifted a metal head into the air, as though smelling, and swivelled its head around and up – focussing on the Doctor and Will.

"What in the name of the saints is that?" asked Will.

The Doctor drew his sonic screwdriver. "A Cybershade. And where there's Cybershades, there's-"

This was the point at which the wooden wall behind them splintered as a tall, armoured figure calmly tore its way through.

"Oh, this is so not fair!" Protested the Doctor, outraged. "Mi-go and Cybermen in one day? All we need now are Daleks, just to make this a party!"

Throughout all of time and space, three things are certain: death, taxes, and the fact that, on any given day, on any given planet, people of any given species will walk right past a tall blue box.

The Doctor likes to think that it's because of a low-level perception filter generated by the TARDISs chameleon circuit, and it's true that TARDISs were designed for such abilities – he also conveniently forgets that the circuit hasn't worked properly for five hundred years. Occasionally, for a space between 1929 and 1994, it blends in perfectly in the city of Glasgow, leading to at least one curious and amusing incident involving a Glaswegian safe cracker, the Strathclyde Police force, and a Thunserian Fire Jackal. But really, when all is said and done, there is something to be said for good old human ignorance. Or it would be, if it only worked on humans.

Parked on the corner of Fleet Street and Chancery Lane, the TARDIS simply stood, tall and blue, as the assembled peoples of London thronged about it, not giving it a moment's notice. Merchants, bricklayers, carpenters, bakers, people going about their daily lives who had no time for an oddity like a blue wooden box on the corner of the street.

One man stopped, though. A hooded man, face obscured by deep shadow. And though nobody could see his eyes, and gave him a wide berth, he looked straight at the streetcorner – at the object that deflected the eyes of others, that seemed invisible and not.

Five minutes later, the people of London have a better reason not to see a blue police box.

This is a house. It is not especially unusual – like practically all structures in the world at this time, it is made of mostly wood, with a few iron nails. Inside it are various pieces of furniture, such as tables, chairs, and, perhaps a bit out of place, a hatstand by the door. Someone obviously lives in this house – the windows are open, the curtains shut. A few cured meats hand from the rafters, and the floor is covered in a large bearskin rug, perhaps recovered from the bear baiting rings nearby. A few tattered holes in the skin attest to this.

This is, however, one very unusual thing about this house. Well, two if you count the total absence of any kind of bed. Or the dim light that basks its interior without any visible source. Okay, three things.

The third is the person occupying it.

The light is not strong enough to banish the shadows, which seem to creep across the floor and walls of the house. But even they have enough sense not to approach the figure sitting in front of the hearth, gently stirring a pot with a long wooden spoon as it bubbles away. She – for the figure appears to be female – leans in close to the rising steam coming from the cauldron, and mutters to herself in a strange language.

The houses to either side of her are dark, their occupants having learned long ago not to interfere in her business. A band of Puritans strode through the street once, handing out pamphlets urging the people to repent of their wickedness and to reject Popish frippery. One brave soul ventured to knock upon her door. Nobody ever speaks of what happened next.

The vapour continues to rise, a pale, ghastly green, wafting up into the figure's nostrils as she continues to babble. She opens her eyes, and begins to cackle, long and hard. She has seen things in the smoke – the oncoming storm, who fought the horror king and won and lost so far off and so long ago; the word smith, to whom words and ideas are but playthings, a power her people have always respected; and the great monarch, sitting in her cage of stone and status, looking out upon her world. And above it all, she sees the nightmares to come, and the madness that shall follow in its wake, and she delights in her own madness for soon she shall be joined in it.

The neighbours rattle their windows softly, making damned sure they're completely shut, and draw the curtains tighter, fingers curled around lucky pendants, crosses, rabbits feet, and even, this late into the Reformation, a rosary. And still she cackles, because the witch Acrasia knows that nobody and nothing can stop its coming.

Early evening in a rural English countryside. Not quite the same England as that inhabited by the Immortal Bard, but not so different as one would think – a few hundred kilometres to the north, and most of the old ways of life still remained, though the fashions and language might have changed a little.

By this time, most people were already indoors, inside their homes or the local pub, to get away from the cold. There's be a frost in the morning, which wouldn't be good for the crops. So it is unsurprising that nobody was there to hear the strange, unearthly sound emanating from nowhere in particular. Though if they had, they would have described it as a rhythmic wheezing sound, or like the grinding of cogs. If they'd been asked to write it down, they would have written "vworp" a couple of times.

A blue box faded into existence, coming and going and coming again, as though fighting to materialise, and finally decided on concrete existence. The door opened inwards and a man stepped out of the door.

"Here we are! Barcelona! Soccer, wonderful beaches, the 2058 Olympic Games, and the meter bar! And if you're very lucky, I'll see if I can introduce you to Peter Mechain!"

He was different to the Doctor. Well, the other Doctor. He was tall and skinny, they had that in common. And messy hair. They had that too. But this man wore a tweed jacket, a bright red bowtie, suspenders and, perched precariously atop his head, a red fez with a tassle. But nobody who had spent time around the two would ever dispute that he was the Doctor – he had the same eyes, the eyes that either belonged to a young man with an old soul or to an old man with a young soul. The eyes of a Time Lord.

There was also the small matter of him having a TARDIS shaped like a police box, which also tends to rule out other identities.

A woman followed after him, grinning madly – a grin which faltered as she took in the sights. She was short, had dark black hair, and wore a look of weary amusement as she looked around and asked wryly,"Barcelona, right? Do they usually have fields where the beach is meant to be?"

The Doctor rolled his eyes. "Come on, Pond, I can't have gotten it wrong this time! I tweaked the temporal differentiators, and totally replaced the special actuators just so I could take you here! Those actuators cost an arm and a leg! Though not literally. Though that can sometimes happen."

There was the babble of words, too. They both had that in common. In fact, someone who knew both Doctors might not think they were as different as they seemed.

He paused, sniffed, stuck out his tongue, licked his finger and tested the wind, and said, "There! I know exactly where we are!"

"It's not Barcelona."

"No, it's Warwickshire," he said proudly. He processed his statement for a moment, running it back in his head. "Hang on, why are we in Warwickshire? This wasn't supposed to happen!"

Clara Oswald rolled her eyes. "Yeah Doctor, so you keep saying." But there was still a trace of amusement in her voice.

The Doctor frowned as they both headed toward the nearest fence. "I'll bet it was the actuators, I knew they should have cost more. The next time I see that pudgy blue man he's going to regret selling me dodgy actuators!"

Clara patted him consolingly on the back. "There there, Doctor. Let's just pop into the village, check the date, and then get back to the TARDIS is nothing interesting happens around now."

The Doctor snorted. "Its rural England, Clara, hardly anything interesting happens here until World War II, and I don't thing you want to be there for that. Well, except for that incident with the Daemon. And the Buddhist monastery. And that quarry with the stone hand. And the lighthouse. Actually, never mind, we should check anyway. Just to be safe."

"Mm-hm," hummed Clara. "Just you remember, I don't want to be in Warwickshire for weeks, like that Fortinbras fiasco."

"I got you back in the end! And you did say you were bored!"

"Being kidnapped by a gang of invading Germans wasn't what I had in mind!"

"In my defence, it wasn't what I had in mind either!"

"No, you were trying to take me to Arcadia, and you got 'lost' along the way!"

"I'm never lost! I know exactly where I am at all times!"

"It's getting to where we want to go that's the trouble!"

And so it continued as they trudged into town. By this time, Clara had noticed the settling cold and started shivering. Still in full-blown self-defence mode, the Doctor whipped off his tweed jacket and settled it around her shoulders – and Clara, still complaining about the Doctor's driving skills (or lack of them) accepted it with a quick smile. It was a well-rehearsed action, and it spoke volumes to the nature of their relationship – if anyone had been there to see it.

In fact, there was someone there to see them pass by. Or, rather, something – a small floating sphere, hovering silently above the treeline. It tracked their movement, giving them a passing scan, quickly classifying them as of little interest – humans, or at least humanoids, in attire that suited a level-two planet such as this. It didn't bother with an active scan – non-humans wouldn't bother trying to blend in, it's programming reasoned, and their presence would be accompanied with loud noises and flashes of weapons. Instead, it moved gracefully across the countryside, ignored by the two people currently bickering as they headed into town.

Somewhere else, a man freezes in shock. And as he tracks the newcomers with eyes that are not in his head, he mutters to himself, "He comes, my Lord! He has brought it!"