She's not his subordinate, not anymore. Neither of them is breaking any rules. Provided they both kept their stories straight about when, exactly, this all began there was no reason to hide.

And yet they both invent excuses anyway; he has to meet with the liaison from Geneva, she has an astrophysics conference to attend. He still drives out to Cambridge to meet her, just a friend offering her a ride in a pinch.

He still discreetly changes into his civvies just before he leaves, before anyone can ask him why.

They still find a junction along the M11 they haven't taken before, at least not for a while. Miss Shaw has an excellent memory; she can still remember which motels they've stayed in already, and find one that's new, where no one has seen them before.

He keeps many secrets: launch codes, radio frequencies, combinations, the location and assemblage of the most dangerous alien artifacts ever to find their way to Earth. Secrets that could undo UNIT, Great Britain, the world if untimely divulged.

This secret – their secret – doesn't belong to UNIT. Only to him.

They don't talk much on the way there, mostly just pleasantries: she asks him about the goings-on at UNIT, he asks her the same about her studies. She's finishing up her research project, apparently, and the report's pending publication. He's proud to hear it even though he has no reason to be; it's got nothing to do with him, after all.

They never talk very much on evenings like these. He never feels like he has to; she doesn't expect him to. There's something about the quiet and the monotony of the ride, their destination clearly in mind, that calms his nerves. He has time to think, here, and no one will demand to know what he's thinking.

And yet it's the time spent with her as well, alone. He does miss her a bit, though he doesn't like to admit it to himself. He misses her sharp tongue and her keen intellect and the way she always seemed to know what she had to do even when she didn't. Much the same show of certainty he had to put on, come to think of it.

He misses the way she never seemed to know whether to take him seriously or not, because it was a great relief not to be taken seriously every so often without imperiling the entire social order of a military society.

But as much as he'd like to hear her speak, watch her think up some counterpoint to whatever he'd said, their tiny quiet space inside the car, like the tiny hotel room, was a sanctuary, removed from the divisions of authority and subordination that neither of them could completely forget. And if they talked they might argue and if they argued all those old shackles would tug at them anew - the uniform he once wore in her presence, her vast understanding of the universe and the authority that came with it, the awkward middle ground between him and the Doctor that she so often found herself stuck in, whether she wanted to be there or not.

They're not easy to navigate, these little oases, but they're preferable to the alternative.

They always get a single room with a single bed, and sometimes (like tonight) he kisses her slowly on her slim, clever mouth where he knows the night clerk will see him, and it chills him to know he is being watched and that the watcher doesn't know him, doesn't care who he or this other woman are - he and Miss Shaw are spouses, lovers, strangers for all he knows. Certainly he was never her commanding officer and she never, ever called him "Brigadier".

She still uses his title to address him even during the car ride, but so soon as they reach the hotel lobby it's always a teasing, thrilling Alistair - she smiles when she says it, seems to taste how forbidden it is.

It took him a few tries before he could remember to call her Liz.

-

He never can quite predict her. Some days she is forthright, almost businesslike, undressing so soon as the door closes and barely answering his touch, finding the easy familiar places on his body that she remembers without having to think. Some days she feigns struggle, wriggling out of his grasp until he has to pin her against the door even to kiss her, and even then her hands resist him, pushing at him, the pinprick of her fingernails spurring him on (like she could never do back then, because the penalty for striking an officer...).

And some days - today, for example - she falls between the two extremes. Some days she pushes him backward onto the bed, lazily unbuttons her blouse, and says with a smile, "You know, I almost missed you."

"You're getting sentimental," he teases, pulling her towards him. They don't bother to turn down the bed; in the morning someone else will come by and wash the sheets and straighten them, erasing them from this room and this building. He finishes unfastening her shirt, lets her luxuriate as he traces her over, remembers (he always remembers; it's part of the secret, too important to forget) where to touch her to coax that satisfied purr from her throat.

"Nostalgic, maybe," she answers, and her sigh in his ear might just be the start of a laugh.

-

She lies down beside him when it's over, close enough that he can hear her breathing slow and settle but not touching, her arms drawn across her body. He doesn't touch her; he thinks he might like to, but holding her afterward seems too typical, too much like something that someone like him is supposed to do.

This isn't typical, whatever it is they have. It's separate, disentangled from both of their lives, a moment or two to step outside their uniform and their lab coat and have something that's just theirs, privileged to nobody else's eyes.

Just before she falls asleep he plays with a lock of her red, red hair, his fingertips just missing the skin of her cheek. She doesn't reciprocate, doesn't even open her eyes, but she does smile.

Maybe it's enough, just keeping a secret for a secret's sake.