After reading so many Human Nature/Family of Blood AUs, I started thinking about the Time Lords and the Chameleon Arch, and how it couldn't possibly be designed JUST to turn Time Lords into humans, considering how many planets and societies exist in the universe. I found the idea that the Doctor could technically probably turn into any species to have some hilarious (to me) implications, and this is what came of that!
I own nothing of Doctor Who - especially not the lines I borrowed from the original script. This work is for fun, not profit!
Martha dashed onto the TARDIS, cringing at the sounds of explosions behind her. The Doctor followed, ducking as he ran.
"GET DOWN!" he yelled, pushing Martha out of the way as a streak of green light blasted through where her head had been just a moment before. Staying low, he slammed the TARDIS door shut and rushed to the console, manically flipping levers and pushing buttons, flying around the round control panel as though their lives depended on it. Which, based on Martha's experiences travelling with the Doctor thus far, they probably did.
"Did they see you?" the Doctor shot at Martha, eyes wild, flipping more levers.
"I don't know," Martha admitted, still gasping for breath.
"But did they see you?!" the Doctor reiterated, sounding panicked.
"I DON'T KNOW! I was too busy running!" Martha shouted. When the Doctor spoke again, he overennunciated each word, as he only did when things were deadly serious.
"Martha, it's important. Did they see your face?" Martha thought back, picturing how the Doctor had pushed her back toward the TARDIS; how her face had been ducked and her arms over her head as the ran, shielding herself from falling debris.
"No, they couldn't have," she answered resolutely. The Doctor sighed with relief and grinned maniacally.
"Off we go!" he announced, dramatically flipping one last switch on the TARDIS's console. The familiar wheeze sounded and the ship began to dematerialize. The Doctor's relief was short-lived, however, as his eyes tracked quickly back and forth along one of the console's screens. He gripped the sides of the screen with white knuckles and let out a frustrated exclamation.
"They're following us!" he spat out. Martha was shocked.
"How can they do that? You've got a time machine!"
"Stolen technology," the Doctor scowled. "They've got a Time Agent's vortex manipulator. They can follow us wherever we go, right across the universe. They're never going to stop, unless... I'll have to do it. Martha, you trust me, don't you?"
"Of course I do," Martha answered without hesitation.
"Because it all depends on you," he continued as though he hadn't heard her.
"What does?" Martha asked, worried. "What am I supposed to do?" The Doctor pulled an ornately engraved old fashioned silver pocket watch from one of his bigger-on-the-inside pockets and shoved it at Martha, closing her fingers over it.
"Take this watch," he told her, holding her fingers closed and staring deeply into her eyes, "because my life depends on it. This watch, Martha - this watch is going to hold everything I am and keep me safe while I go into hiding." Martha looked at him, scared and confused.
"What do you mean?" she asked him.
"Time Lords had a lot of technologies beyond those of humans. You've seen our spatial-temporal advancements. Well, there's another invention on the TARDIS that I hoped that I would never have to use," the Doctor explained, dropping Martha's hand and beginning to pace. He ran his hands through his already chaotic hair, his stress evident. "Every so often, it was necessary for a Time Lord to camouflage themselves - to go so far undercover that even they themselves were not aware of who and what they were. They invented a machine called the Chameleon Arch. It overwrites a being's biology. It's designed so that the Time Lord in question can blend seamlessly into any society, hiding in plain sight until it's safe for them to emerge."
"Okay…" Martha said as she tried to process this information. "So this Arch thingy will turn you into something else so that those things that are following us can't find you. And since they didn't see me, I can stay with you and they won't be able to track me, either. But what's the watch for?"
"The watch will hold my Time Lord self," the Doctor explained. "All of my thoughts and memories, all of my genetic material, everything needed to turn me back. The Family - the aliens that are tracking us - they only live for three months. They're like mayflies. So I'll use the Arch, hide for three months as someone else, and then at the end of those three months you'll open the watch and I'll come back to myself. Okay?" Martha's lips tightened in worry, but she nodded.
"Okay," she answered resolutely.
"Now this is going to hurt," the Doctor warned, "so try not to be alarmed. Do not interfere in any way. When the transformation is complete, you'll know. I've set the TARDIS to search for a time that is safe; once she lands, you can use the psychic paper to set yourself up for the next few months. I trust you take care of me, Martha, and make sure nothing happens to either of us."
"What if something goes wrong? What if they find us?" Martha asked.
"If you or others are in danger, if you absolutely have to, you can open the watch early. But you're brilliant, Martha. I trust you to keep me safe." Despite herself, Martha smiled a little.
"Okay," the Doctor said with a deep breath, "no use putting it off." A strange metal helmet resembling a cage had dropped down from the ceiling of the console room. The Doctor pulled it over his head and closed his eyes. Shortly, he was screaming, hands clasped to the helmet, body curving in pain. Martha stepped back from him quickly, scrunching her eyes shut, pushing her hands into her ears, trying in vain to distract herself from the Doctor's distress so that she didn't rashly interfere in the transformation process. Who knew what would happen if she disrupted the process early? After what felt like days but was likely just moments, the screaming stopped, and the room went eerily silent. Cautiously, Martha opened one eyes and then the other, dropping her hands from her ears.
The Chameleon Arch helmet dangled from the ceiling, swaying slightly. The Doctor was nowhere to be seen. Martha dashed to where he had been, scanning the room in panic. What had happened? Where was he? Before her fear could grow into hysteria, however, she looked down at the floor.
A medium sized green lizard looked up at her, bulbous eyes rotating at slightly different angles. As she looked on in disbelief, the lizard slowly unrolled its tongue at her and its skin began to shift from green to grey, blending with the metal grated floor.
"Oh you have GOT to be kidding me," Martha breathed in despair, crouching down and picking up the lizard with both hands, lifting it to her eye level. "When you said you'd blend in, I didn't think you meant it QUITE so literally. What the hell am I supposed to do with a chameleon for three months?!"
As though in answer to her incredulous question, Martha heard a "pop!" and a largeish glass tank appeared on the floor in front of her, containing an arrangement of branches, plants, rocks, and dirt, as well as a complex light and water system. Martha sighed and placed the lizard into the terrarium, sliding the lid closed. The TARDIS shuddered to a stop (much more smoothly than when the Doctor was actively piloting, Martha couldn't help but notice) and Martha stood, making her way to the doors and peering out.
To her relief, Martha was greeted by the familiar sight of her bedroom in her own London flat. It was just as disheveled as when she had left with the Doctor; the evidence of her busy schedule as a med student visible in the untidy stacks of papers and books on her desk and floor, as well as the unmade bed and array of dirty coffee mugs. She haphazardly cleared a spot on her desk, and then returned to the TARDIS, hoisting the heavy tank with a grunt and hauling it the few feet down the ramp and into her room. Thumping it down heavily on her desk, she closed and locked the TARDIS doors behind her before logging on to her laptop to see how long she'd been gone.
"Oh, thank god," she exhaled when she realized it had only been a few days since she'd last seen her family. She could easily integrate back into her class and training schedule for the last couple months of the semester, killing two birds with one stone: hiding the Doctor, and continuing to work toward her almost-complete degree.
Two months into their three month stint in London, a green flash in the sky caught Martha's notice as she was walking back to her flat after a shift at the hospital. Although she couldn't be sure if it was anything to worry about, Martha decided to err on the side of caution.
"Come on Doctor," she called to her pet chameleon as she dropped her keys on the table by the door and walked into her bedroom. "Time to go on an adventure." She transferred the lizard into a travelling case that she had purchased for just this possibility, changed out of her scrubs into street clothes, grabbed an overnight bag that she'd kept packed just in case, picked up her keys and purse, and headed out of her flat, locking the door behind her. She and the Doctor were off to do a little traveling.
Martha and the Chameleon Doctor spent the last month of their exile from time and space travel on a leisurely tour of the British Isles and Western Europe by train and boat, stopping at pet-friendly hotels in different cities where the Doctor could bask under his heat lamp while Martha took in the sights and sampled local cuisine. Aside from having to learn how to procure insects for the Doctor to eat in a handful of languages, Martha didn't have a bad time of it at all. Nothing suspicious bothered them.
At the end of the three months, Martha opened the watch, the Doctor returned to himself, and the two of them journeyed back to London and the TARDIS, ready to explore the stars.