It's not as though the concepts of 'day' and 'night' truly exist in a place like the TARDIS, not bound by the ordinary confinements of pesky little things like time, but Jamie finds that their interludes between adventures somehow still seem to fall into patterns of days. It isn't something he thinks about often, but rather a thought that strikes him one 'night' as he and Zoë manage to yawn simultaneously before wandering off to find their respective beds. As he settles his head onto his pillow (it's stuffed with a squishy substance that he can hear Zoë's voice calling "memory foam", whatever that means) he wonders idly if the Doctor, too, has felt that subtle shift in the atmosphere that drags on the eyelids of their human companions. The lights in his room have gone dark, he notices, as they always do when he sleeps - he's sure the Doctor and Zoë would have a scientific explanation for this phenomenon, but is seems like magic to him - nut his curiosity grows, and he rouses himself to look into the corridor to find that it has become dim as well.
The Doctor lays awake on their bed. They don't need sleep the way that Jamie and Zoë do (the image of Jamie struggling to stay awake after the trio had finally made it back to the TARDIS and greedily eaten their first real meal in three days swims to the forefront of their mind, and they smile), but a few hours of rest is certainly beneficial, and, since the TARDIS is functioning properly for once, they've decided to indulge themself. Coat, trousers, and shirt casually hung on the coat rack that had once adorned the console room before a particularly rough landing had revealed how dangerous heavy, unsecured objects could be to travelers, they stretch out on the mattress and close their eyes.
Not five minutes later, the swishing noise of someone trying and failing to open a door discreetly jolts them back into awareness, and they open their eyes a sliver, trying to identify the intruder without alerting whoever it is to the fact of their consciousness. A small jolt of surprise hits them as they recognize Jamie's face; he wears a mixed expression of curiosity and nervousness (and the pair of loose boxers he had taken to wearing at night after a rather traumatic incident involving an open door and a horrified Victoria) as he approaches their bed. The Doctor opens their eyes, and they see him tense.
"Jamie?" they whisper gently.
"Ah, sorry, Doctor, I didn't mean to wake ye!" Jamie's tone is hushed, but he sounds slightly distraught; whether it is from waking the Doctor or being discovered, they cannot tell.
"Might I ask what you are doing here?"
Jamie looks down. "I was just, ah, wonderin' if - well, if you were asleep, like Zoë and me. If you slept at the same time as us, is all."
The Doctor smiles and sits up. "Well, I was about to sleep when you walked in." They're perfectly aware that it's not the full answer to Jamie's question, but, judging by his blush, they doubt that he is in the mood to hear a long-winded explanation of the sleep patterns of Time Lords.
"Sorry."
"Not to worry, Jamie. I don't mind." They smile again. "But you might want to work on your stealth tactics before you walk past Zoë's room again. I doubt that she would be so forgiving, especially since she's barely gotten a wink of sleep in three days."
Jamie tries to make an indignant noise in protest, but his body, suddenly reminded that it, too, has gone too long without sleep for its liking, stifles the noise with a massive yawn, which Jamie hastens to cover. The Doctor pats the space next to them in invitation, and, though Jamie seems surprised at the gesture, he slumps down gratefully into the soft material. "You wouldn't mind if I just rest here for a second, would you?" he asks, his original query forgotten as exhaustion settles in his bones like lead. He looks up at the Doctor's face in askance to see them returning the gaze with warmth, a small smile playing at the corners of their mouth.
"Not at all." Just a second, they think, suppressing a chuckle as his eyes close and his body relaxes. Oh, Jamie. They fondly lay their blanket over his sleeping form before reclining and closing their own eyes. As they drift off, they feel Jamie's warmth move closer and his hand close around a handful of their undershirt as he snuggles up to their side.
The TARDIS, attuned to her human inhabitants' sleep cycles, brightens her lights as they begin to stir. The Doctor, already awake, smiles as the figure still clinging to their side burrows his head defensively into their neck and slowly rubs a circular pattern on his back with their thumb. Jamie's warm scent, the tang of soap from last night's shower mixed with a mustiness that is so human but so uniquely his, washes over them anew, and they can't help but hope that this situation might repeat itself.