In canon terms, I set this after Midnight for Doctor Who and some point before Morgana turned bad in Merlin.
"Here we go Donna the tenth of October 2010." The Doctor flung open the doors of the TARDIS in excitement and looked at a watch on his wrist. "and its 7 minutes past 10"
"So" replied Donna putting her hands on her hips "you've took me to Pompeii, the Ood sphere and the planet Midnight and now here we are... a year in the future, Why?"
The doctor looked insulted "but 10:10 10-10-10" he replied "isn't that exciting to you and it's almost here in two whole minutes"
"What about 2222 that's an exciting year, we could go to the 2nd of February if you want to be pedantic about it."
"Nope" replied the doctor, "that's a boring day seen it to many times before. Now today!" he held his arms apart and looked out the open door "Today I've never seen" he flung his arms into his pockets and strode outside.
"A museum, you've took me to a museum in 2010" Donna exclaimed, she paused and looked at the sign 'Manchester Museum of Science and Industry' "A museum in the north!"
"I like it, so shhh.." The Doctor started to walk towards the door, "you coming?"
Donna sighed in defeat and started to follow the Doctor, all of a sudden she felt dizzy like she'd hit a wall of something, she couldn't walk any further and swayed for a moment before fainting.
The Doctor had reached the front door of the museum as he realised his watch was beeping, "There you go Donna Ten past ten. Exciting huh?" There was no answer "Donna?" He span around and Donna was gone.
A strange noise awoke Donna, she felt wet and was laying in something that felt gloopy, mud? It was raining she could feel it on her face, she shivered and opened her eyes, "Bloody north" she mumbled looking up at the gray cloudy sky.
There were some shouts from somewhere around her at which point Donna sat up and saw she wasn't alone, ahead of her stood a horse coming out of the forest, forest why was their forest? Donna tried to stand up but still felt dizzy.
"Whoa there" called a voice, a figure who sat on the horse, it took Donna only a moment to realise he was in chain mail looking very much like a knight.
"My knight in shining armour" Donna called "Where's the Doctor?" she said before feeling faint and passing out again.
"Donna" called out the Doctor again he looked around immediately spotting a scorched mark between him and the TARDIS. He ran over and slipped on his brainy specs to investigate. "Transmat" he concluded "a rather crude one at that" holding up the sonic he did a quick scan of the air "now where did you go Donna" the sonic beeped once "out of range brilliant, she could be anywhere. I hope she's still on earth" the thought of Donna alone on another planet worried the Doctor not just because of the danger but because of Donna, she hadn't quite got the hang of off world diplomacy yet.
The Doctor stepped into the TARDIS and continued to scan for Donna, again nothing. Groaning in annoyance he wacked a control causing a plume of smoke to rise from the vents below him as if the TARDIS were trying to say 'stop it'.
"Sorry old girl" said the Doctor as he started to head for the door, transmit beams like this only worked if the source was nearby he looked at the monitor displaying the museum and the only logical concussion was that it was coming from there.
The next time Donna awoke she was somewhere considerably warmer although not as comfortable as the mud had been.
"Where am I" she managed to croak, she was passed a jar.
"Drink" an elderly voice spoke, he sounded caring and soft, Donna drank the water.
"Merlin, look after the Lady" said the elderly voice, "I need to go ensure the king does not assume the worst of her"
Donna managed to sit up and examined her surroundings, stone blocks peaked out from peeling brown plaster on the walls which were lined with shelves filled with bottles, books and stacks of paper. The whole room seemed full of stuff and lit with candles on the walls and tables, wherever she was Donna had the distinct feeling she wasn't in the 21st century any more.
Back in the museum the Doctor had flashed his psychic paper to the ticket desk, it had announced him as a trustee and he was now receiving a very much unwanted personal tour from a lady who had introduced herself as Nora.
"Nora?" he asked
"Yes"
"Are there any scientific research projects going on in the museum now?"
"Oh of course not", she replied "that all happens at the university, I could arrange for a college to take you there if you want"
"No thanks" this was useless he thought, he'd been wasting precious time following this lady around and as nice as she was the bioelectronic trail Donna would have left behind was getting weaker every minute"
Donna looked at the skinny boy stood before her, he returned the stare "what?" Donna finally said "are you looking at?"
"Where are you from?" he whispered "you dress so strangely"
Donna looked down at her leather jacket and jeans "not as strangely as you" she shot back "where am I?"
"Camelot" he replied
"Camelot!" Donna exclaimed before realising something "Did he say Merlin!"
"Yes, that's my name" the skinny boy looked confused.
"As in Merlin and King Arthur and the knights of the round table" she paused "aren't you supposed to be old?"
Merlin looked at Donna in shear confusion "I'm only 17"
The door swung open and a tall blonde man with a strong physical build strode in "Merlin, has the lady awoken yet?" he spotted Donna who was staring at him.
"I am Prince Arthur, welcome to Camelot" he announced.
"Disney has lied to me" Donna concluded.
The Doctors tour had finally finished as he was led to the front reception again "would you like me to call my college at the university?" Nora asked.
"Yes please" smiled the doctor.
"One moment" she said and walked into an office. Realising this was his chance The Doctor ran around the corner and strode towards the door he had passed earlier with a big 'private' sign.
One flick of the sonic screwdriver and the door opened to reveal a small maintenance closet. "I'm not falling for that one" he said out loud and swung open a metal cabinet to reveal a set of stairs. "Easy" he grinned and headed down.
An alarm sounded as the doctor unlocked a door at the base of the stairs and he heard the familiar noise of guns being cocked.
Donna stared at Prince Arthur for a moment longer, "where am I?" she asked again
"Camelot" Merlin repeated.
"No no, I'm in some kind of fairy tale, what planet is this?"
"Earth" Arthur answered
"Year?" Donna flinched as the answer came.
"1010" Merlin answered.
Donna sighed "brilliant, just brilliant"
"Please no guns" the doctor said
"Stand down" called a voice, a lady stepped out of the shadows wearing a familiar red beret, "Doctor, what a surprise"
"I'm sorry, I haven't met you yet" the doctor said stepping forward "Sergeant?"
"Cornel Erisa Magambo" she stuck out her hand, the doctor ignored it.
"So what is Unit doing under this museum then? I assume it must be big from the welcome I just got"
"I think you'll like this" she said and began to walk. The Doctor followed, rolling his eyes soldiers thought they ruled everyone didn't they.
They entered a room in the centre of which stood a rather crude looking teleport device the doctor ran over to it "where did you find this?"
"We made it" she replied proudly yet seeing the doctors expression, the smile faded from her face.
"Then tell me what does it do?" he asked her
"It moved objects, extracts them from the past, the year 1010 to be precise"
"No it doesn't" the doctor replied "shall I tell you what it does?"
Magambo nodded.
"It swaps items" announced the doctor, "a cup for a cup" he said picking up an ornate metal cup sat on the side, "a bowl for a bowl", he picked up a wooden bowl tossed in casually in the air, caught it and sat it next to the cup, "a person for a person." He stared at Magambo who sighed.
"Follow me" she said.
They walked down another corridor until reaching another locked door "she arrived an hour ago, around the time our sensors detected your arrival".
The door swung open to reveal a dark lady with wavy brown hair, she sat defiantly on the cold metal bed.
"I demand to know what's going on" she stood up "My name is Gwen and I demand to be released immediately"
The door swung open again and Donna watched as a lady strode in "Arthur have you seen Gwen?" she asked
"No Morgana I haven't he replied "when did you last see her"
"She was going to fetch some water an hour ago, none of the guards have seen her since"
"The lady Gwenivere?" asked Donna
"Lady" laughed Morgana "no Gwen is my maid servant and she has disappeared"
"Oh" replied Donna, she looked over to Merlin who continued to stare at her "what?" she demanded. Before jumping off the wooden table she had been sat on, "as fun as this little history lesson is, I need to find the Doctor"
"Gaius will return soon" Merlin replied "you should wait for him here"
"Not a doctor, The Doctor, there's a difference" she replied before heading towards the door
"Stop" she heard a voice command, she turned around to see that Arthur had drawn his sword, he looked shaken and worried "What have you done with her?"
Donna froze, she'd never felt so threatened, he looked angry and scared not a good combination on any day.
"Arthur please" Merlin pleaded
"She must be a witch" Arthur said "first those strange objects and now Gwen, she's done something"
"I highly doubt it sire, please calm down, Gwen has probably just got distracted somewhere" Merlin replied, he appeared to be a calming influence on Arthur as he returned his sword "The lady will stay here" he ordered before leaving with Morgan "We shall search for Gwen"
"Objects?" asked Donna after they had left, Merlin passed her a mug from the side, it had the UNIT logo, donna recognised it immediately after her meeting with them recently or 1000 years in the future however you looked at it.
"Ah" she said as she placed it next to the plastic bowl on the side.
"Oh for goodness sake" the doctor cursed "when will you learn to leave this stuff alone till you ready for it. I'm going to take her home."
"Thank you kind sir" said Gwen, she followed the Doctor as he left.
"Artefacts" demanded the Doctor as he reached the lab again, Magambo nodded and a solider passed the doctor the chalice and bowl.
"Oh don't think I'm going for good" he said as he reached the door of the lab, "I'm coming straight back to shut that thing down for good" he grabbed a walkie talkie as he left "I'll be in touch"
Reaching the reception of the museum The Doctor was relieved to see that his tour guide had gone, he didn't have time to be explaining himself or the terrified Medieval woman he was with.
Gwen was sticking close to him and taking it all rather well, "Where are we exactly, sir?" she asked
"Urm.. " The Doctor knew he should be better with awkward questions by now, but she had caught him off guard. "Not far from your home really, just ... let's say a different time that's all and I'm not sir ... well not really, anyway just call me The Doctor"
"I shall" she murmured "a different time..." Gwen pondered this for a moment as they left the great building, It didn't make much sense but this Doctor had promised to return her home, he seemed trustworthy so she kept silent.
Moments away from the TARDIS he felt a buzzing sensation "Transmat" he held the walkie talkie to his mouth "Cornel, turn off the device now" he shouted
"We're trying" came the frantic reply.
"Try Harder" he ordered trying to fight his way towards the TARDIS but it was to late with a shimmer of light and a vrumph noise the TARDIS was gone and in its place stood a cart of hay and a terrified horse.