"Tell me if it hurts you."
She turns her head so that she can grin at him over her shoulder. "That's part of the fun."
"You have a weird definition of fun."
"This from someone who's idea of a good time involves fighting aliens with a screwdriver."
"You're sure you're ready?"
"Go ahead and try me."
For all her bravado, Martha's hand grips convulsively at the bench as the first needle slides in. Tattoos haven't changed that much in the past couple of centuries.
She'd dragged the Doctor in here after noticing all the gorgeous body art that's everywhere in this period. He grumbled about potential anachronisms when he takes her back home, but she managed to convince him, promising not to flash it around. After ten minutes of trying to explain what she wanted to the artist - an alien of indeterminate gender who seems oblivious to the effect of the TARDIS translator - with nothing but hand gestures, the Doctor had taken pity on both of them and yanked the thick black pen out of its tentacle. Martha lay face down with her head pillowed on her arms, shirt rolled up and jeans yanked down, as he deftly sketched a butterfly on her hip.
All that's left is to make it final. It doesn't hurt for long; the process is a lot quicker here and the anaesthetic spray has deadened most of the nerves. She must convince him to bring her back next time she wants a new one done. Within a few minutes, she's looking in the big mirrored wall at the end of the shop, admiring the effect. The wings glow green and gold when the light catches them.
"Lovely," she says, smiling at the tattooist and turning this way and that to watch it ripple and change colour. "D'you like it?"
"It's brilliant," he says, leaning forward to admire his handiwork.
"All right, then," she says, waving at the alien. "You're next."
"No thanks," he says, taken aback. "Haven't had a tattoo in several lifetimes."
Martha raises an eyebrow, and lets the implications go. "Then it's time you had another one. Don't tell me a guy who fights off planetary invasions every other day is scared of a little needle? I promise I'll hold your hand."
"It's not that, I just don't see the point."
"It's a permanent souvenir." When she's back home, taking exams and eating chips, she wants to have something she can look at to persuade herself that all this really happened. "Something to remember this time by."
He shrugs. "Nothing's permanent for me."
"Then you can always get some futuristic laser surgery if you don't like it. Come on, get it off."
She holds his eyes, challenging him, until he comes to a sudden decision. Tie, jacket and shirt go flying and he arranges himself artistically on the bench.
Martha examines the canvas in front of her with a thoughtful frown. He's startlingly pale, all freckles and ribs poking through. She ghosts her hands over his back, trying to decide where the best place would be. At last she reaches out to brush his left shoulder blade. "There," she says. The tattoo artist can at least grasp that one.
"Do I get any say in this?"
"What did you have in mind? Time Lords Rule OK? I heart Shakespeare?"
That raises a smile. "Maybe I'll let you decide, since you're so keen on the idea. Just leave out the spray - human drugs don't agree with me. It'd probably turn me purple or make me explode or something."
She's half-tempted to put a rose on him. Pink, like the abandoned clothes she keeps finding in strange places around the ship, and covered with thorns. Two hearts. A Möbius strip. A snake biting its own tail.
Then she's got it. Earlier in the day, walking through the market, they saw this weird stone box. Martha assumed that the symbols on the lid were just decorative at first, since the TARDIS translator didn't do its usual trick of turning them into recognisable English. But then the Doctor stood there gesturing wildly and muttering about it being impossibly old, until the stall holder demanded that he either pay for the thing or stop scaring away the other customers. Uni has forced Martha to develop a good memory; it's harder to draw the symbols accurately than it is to remember what they looked like. It'll be an enigma tattooed on a mystery.
"What are you doing back there?" the Doctor says, trying to look round at his own shoulder.
"Don't wriggle, or you'll smudge it."
"As long as you're not drawing a Dalek in a bikini."
"There, all done," she says, nodding at the tattooist to ink it in. She crouches down in front of the Doctor and puts her hand over his. "Just be a brave boy for a minute and then you can see the results."
He just barely flinches at the process starts, then smiles. "If you've written something rude, I'm going to take you somewhere horrible next."
"It seems to me we barely go anywhere else." That's not exactly true. Most of the places they go would be perfectly nice if it wasn't for the monster problem, but he seems to get her point.
The alien works quickly - the advantage to having a dozen tentacles instead of arms, she supposes - and soon enough it's all over.
"Go on," she says. "Take a look."
He stands in front of the mirror, craning around to see what she's done. "You do realise that you may have just indelibly written 'this side up' or '94% fat free' on me?"
"You don't like it?" she says, suddenly anxious that he should.
He grins at her, eyes wrinkling up at the corners in that indecently attractive way. "'Course I do. Always knew you had excellent taste."
She's annoyed to find herself so relieved at his approval. "Maybe if you go around showing it to everyone we meet, someone will eventually know what it says."
"Oh, that'll be good. I'll just walk up to total strangers, take my shirt off, and ask them to translate my shoulder," he says, pulling his clothes back on.
She laughs, and reaches into her pocket for a handful of credits to give to the alien. It waves it's tentacles at her in a gesture that could mean 'goodbye', or not.
"It'll make at least as much sense as most of the things you say to people."
"Come on, Miss Jones. I'll buy you a tomato ice cream to say thanks."
"Tomato?" Martha wrinkles her nose. The future has some daft ideas sometimes.
"All the rage this year, and it is technically a fruit. I once spent ages trying to convince the first European explorers in South America that they weren't poisonous, but you know Cortez, never listened to a word I said ..."
Martha laughs and links her arm through his. Whatever happens in the future, now they'll always have the marks they made on each other.