The Doctor and Martha stood in the doorway of the TARDIS and watched the Rani depart. Martha waved, the Doctor didn't.
"So," said Martha, "Donna turning out to be a Time Lord, that was a surprise, wasn't it?"
The Doctor slammed the TARDIS door shut.
---
Later in the vortex, once the Doctor had stopped sulking about the Other Absolute Last of the Time Lords not wanting to stay with him, he turned to Martha and said, "I've been thinking-"
"Oh, God."
"Sorry?"
"I said, oh good."
"Donna was here for ages, ages and ages. And I didn't suspect who she really was, not once. And she's not the first person I've travelled with."
Here comes the R word, thought Martha.
"I've had loads of people here, dozens, well more than dozens-"
"You really know how to make a girl feel special, Doctor."
The Doctor gave Martha his best clueless alien look. He still wasn't any good at it.
"Anyway, the point is that any one of them could be a disguised Time Lord and not even know it."
"I'm not a Time Lord, Doctor."
"I never thought you were," he objected.
"I know you've been looking through my room when I'm not there. And there's no fob-watches, no suspiciously large lockets, nothing."
"I wasn't in your room looking for chameleon arch stuff. I was there…." The Doctor trailed off, realising that 'fondling your knickers' was a bad place to take that sentence.
"And last time we were on Earth you asked mum if I was adopted and she'd just never told me."
"I remember," sighed the Doctor nostalgically, "that was a slap and a half."
Returning to the present the Doctor continued, "The point still stands, any one of the others could be a Time Lord, what better way to make sure they were discovered than to travel with me!"
Martha thought about the suspiciously long amount of time Donna had spent hanging around the TARDIS wearing conspicuous jewellery covered in gallifreyen writing and decided that any fob-watched Time Lords out there might have better luck walking up and down Oxford Street carrying a placard that read 'please open this watch.'
"So you want us to march up to people you used to travel with and say 'hey, do you think there's any chance you're really a time travelling alien stuck in a watch?'"
"I think we can manage to be a bit more subtle than that, Martha."
Martha scoffed at the idea of subtlety and the Doctor existing in the same universe. Sensing that she wasn't warming to his plan the Doctor plastered his most ingratiating smile on his face (the one that made people want to slap him) and bounced on the balls of his feet.
"Oh, go on! It'll be fun, and I just want to find one Time Lord who isn't evil, just one."
"I suppose it can't do any harm for us to go and have a look."
"Brilliant! Fantastic! Lovely! Only the thing is I've travelled with rather a lot of people over the years and it's all right for me, I've got a couple of decades to spare, but you'd get old and die. So how about we split them up, half each?"
This was how two days later Martha found herself standing in the console room armed with a vortex manipulator, a list of the Doctor's former travelling companions and a thermos of coffee.
"Good luck," said the Doctor as the TARDIS vanished around her.
"Git," muttered Martha.
---
Her first visit was to a chain smoking man called Fitz whose reaction when Martha told him about the Doctor destroying his planet was
"What, again?"
Martha was beginning to suspect she should have stayed at Torchwood, admittedly they were a comically inept secret agency but at least most things they destroyed only needed to be blown up once.
Then she met an American named Peri, who unleashed such a torrent of abuse at the very mention of the Doctor that Martha decided that even if she was a Time Lord she was probably one of the evil ones.
On a hospital station hundreds of years in the future she met a woman working to cure this era's version of leprosy. She decided not to ask about the possibility of her being a Time Lord on the grounds that Nyssa had enough on her plate being the last of one species without having the Doctor and the Rani inflicted on her.
---
She used the Vortex Manipulator to get back to the TARDIS. One look at the Doctor's face told her that he hadn't had any more luck than she had.
"Sorry."
"Never mind," he grinned. "We're only halfway through the list, might strike gold yet."
Which brought Martha neatly to a subject she'd been meaning to broach. "Doctor, how did you decide who was on my list and who was on yours?"
"I didn't, it was just random."
"Oh, so it's got nothing to do with the fact that Sarah Jane Smith's got a skinny, brown haired son with no social skills, who's smarter than any human ought to be?"
"What!?"
"If Donna was still around she'd report you to the child support agency."
Mention of the Rani made the Doctor look even more distant and distracted than mentioning Sarah Jane's curiously Time Lord-esque son had.
"I'll just be getting back to looking for Time Lords then."
---
Martha had trouble believing that the woman who'd opened the door of the Cambridge flat was a professor of physics. She certainly didn't look like any Physics professor Martha had ever had, mini skirts not being hugely fashionable among the faculty at her university.
"Liz Shaw?"
"Yes, how can I help you?"
"I-" not for the first time Martha wished for her own psychic paper. She decided to give up on subtlety, no doubt the Doctor already had.
"Listen, do you think there's any possibility that you're really a time travelling alien trapped in a watch?"
Liz looked speechless. And Liz didn't look to Martha to be the kind of woman who was speechless often.
"You must be a friend of the Doctor's, you'd best come inside."
---
Martha sat in the living room, drank tea, and established that Liz wasn't a Time Lord. She didn't have unexplained origins, or re-occurring dreams, percussion instruments living in her head, or any desire to take over the planet. She didn't even own a fob-watch.
"Well, thanks for your-"
Martha was interrupted by Liz's phone ringing.
"Excuse me," said the physicist, getting up to answer it. Martha didn't mean to listen in, not really. But it was hard not to given what Liz was saying.
"Yes, Brigadier, I understand... Cardiff, again? I bet it was bloody Torch- Yes, Brigadier... The whole quarry?... And you're sure it's alive, I'm on my way."
Liz hung up and regarded Martha from underneath a sceptically raised eyebrow.
"How's your chemistry, Doctor Jones?"
---
UNIT laid on a helicopter to ferry Martha and Liz to Cardiff. Martha had to admit that it beat the hell out of the Torchwood SUV.
In a quarry just outside the city some malevolent plant life was growing, it had already crept over the edges of the pit and the UNIT boffins had calculated that if it kept up its current rate of growth then it would reach the outskirts of the city in a few hours and completely overrun it within days.
Brigadier Alistair Gordon Lethbridge-Stewart had already established that it was impervious to bullets and so was very pleased when the helicopter bearing Liz Shaw arrived.
"Liz, good of you to come," he greeted her, looking enquiringly at the young black woman who'd followed Liz from the helicopter.
"Oh, Brigadier, this is Doctor Martha Jones, she's a friend of the Doctor's. She's from the future," Liz's voice tinkled with laughter as she said that last bit.
"Ah, well, lovely to meet you Doctor Jones, any help you could offer would be gratefully accepted."
"Sure," Martha shrugged, "happy to help."
"We've got you a sample of the plant, although it took some doing. Bloody thing nearly took off Benton's hand," he nodded at a young dark haired soldier with a bandaged hand. The soldier smiled and waved at Liz and Martha.
"We've also set you up a lab."
Liz followed the Brigadier's gaze. "A tent by a quarry, and people told me that life as a scientist wouldn't be glamorous."
---
"The plant might have been impervious to bullets but it was all too susceptible to certain types of chemical weed killer.
Liz, Martha and the Brigadier watched the plant as it withered and retreated back into the quarry to die.
"Marvellous work Professor Shaw."
"Oh, it was all Doctor Jones' idea."
"I only had the idea it was you that figured out how to implement it."
"As much as I hate to interrupt this mutual professional admiration society," interrupted the Brigadier. "Geneva will be after me for the paperwork about this incident."
The Soldier with the bandaged hand; Benton, Martha remembered, strolled up to them. "That was quite something, Miss Shaw, you too, Miss Jones. We're all going to the pub to celebrate if you want to come?"
The Brigadier cleared his throat.
"We're going to fill in our paperwork," Benton corrected. "Then go to the pub."
"I'm sure Martha has to be getting back to the Doctor."
Martha looked at Liz, then Benton, then the rest of the UNIT boys, then at her vortex manipulator and back to Liz. She smiled, "I suppose he won't miss me if I go for a quick drink."
---
The Doctor was beginning to worry about Martha. She hadn't been back to the TARDIS for weeks. He hoped her vortex manipulator hadn't broken down, it would be awfully difficult to find her when she could be anywhere in time and space.
It occurred to him that maybe she had simply decided not to come back. After that business in 1913 and then the year that never was perhaps using her as a human Time Lord detector had been a bit much?
Nah, he dismissed the idea, Martha wouldn't leave him. Not Again.
At the sound of a vortex manipulator he made a dash for the console room. He didn't find Martha there but he did find a post-it fluttering slowly towards the console. He snatched it out of mid air, written on it in tiny, neat handwriting:
Dear
Doctor, Good luck with finding more
(non-evil) Time Lords. Will try not to do anything terribly
anachronous, like inventing time travel. Love Martha
Jones P.S Liz says to say hello and that she thinks she knows
what was wrong with your TARDIS all that time you were stuck at UNIT
if it's still any use to you.
Have decided to stay with Liz as I have been here almost
a month and she has yet to ask me to walk round the planet telling
everyone how brilliant she is.
The Doctor sighed. There went another companion. This regeneration was certainly going through them.
Oh, well, he still had a few more of his former companions to visit. He consulted his list to see who was next. Jamie McCrimmon. With a manic smile the Doctor sent the TARDIS spinning on through the vortex.