He works. There's always something on the TARDIS that could use fiddling with–it almost seems designed to fit his mood. He can always be turning something, or pulling something, and he can pay attention to that instead of whatever's bothering him.

It's more intense at these times, the reminder that he's the last Time Lord, that he's the only one awake, all alone with his TARDIS. He remembers all he's lost, his home, his friends, his family. Every day, it seems, he remembers someone new that must be dead. The TARDIS is some comfort, a piece of his homeworld. That's why he spends the long nights with her, listening to her hum. He feels better when he's with his ship and it holds him over until Jack and Rose wake up and he can pretend for another few hours that he's not alone.

He reads. There are so many choices in the TARDIS library, even he can't get through all of them. Scientific texts and good literature and things he reserves for when he sits up in bed with them, but when he needs to be alone, or when Rose kicks him out because he leaves the light on, he goes to the library and reads something stupid.

Jack and Rose would never let him live it down if they caught him reading trashy romance novels, but he likes them because they're so human. He can get lost in those worlds because they're so unlike his own, for the same reason Rose says Mickey loves science-fiction. It's the kind of life he can never have, and he wonders idly if he'd like to have it, even just a taste of it, that street corner, two in the morning kind of life.

He thinks. He's a genius and he knows it. He loves his mind. Sometimes he can just think for hours on end and come up with new ideas. He comes up with things he'd like to show Rose and Jack and things he's sure he wants to keep away from them. He comes with ideas for fixing things wrong with the universe, ideas he'd surely implement if he could just pop home and get some backup.

Then, he thinks of all the things he's done wrong, all the ways he could have saved Gallifrey, saved everyone; if he'd just been a little faster, a little cleverer, he could have done it–he's a genius, right? And because he couldn't think of a way out of that situation, he'll never be able to stop thinking. He thinks of a way to protect Rose and Jack should the unthinkable happen. He makes plans, morbid plans, but he doesn't think he can live with himself if he loses one more person.

He wanders. The TARDIS is so big that he doesn't even visit everywhere regularly. He hasn't been in the art gallery in years, so he goes there sometimes. He tries the ballroom some nights, but he doesn't like the way his footsteps echo in the vaulted ceilings. It might be nice for dancing, though. He'll have to dust it off.

He can't look at the bedrooms of those he's lost or left behind, though. He's keeping them just the way they were, just in case. He doesn't like to think about how he might one day have to close off Rose and Jack's rooms. He decides to be extra careful with them, but at the back of his mind, he knows he's just not that clever. So he doesn't think about it, and goes back to the ballroom and stands in the dust.

He listens. He stays in bed between them and listens. Usually, Jack's asleep first, his breathing growing shallow, and then Rose follows, breath whistling a bit. They're touching him, her hand tucked in his or Jack's arm around his waist, their bodies on either side of his two warm reminders that they're human, separate from him. Sometimes, he doesn't know how they can stand it–Rose has cold feet and Jack hogs the covers–but they seem quite attached to this sleeping thing.

And, gradually, the Doctor finds he likes this option most of all. It's more comfortable, for one thing, than lying on his back underneath the console, and he likes watching them, wondering about their dreams, listening to the beat of their hearts which, combined, equal his two.

And sometimes, just sometimes, one of them wakes early, usually Rose (but sometimes it's Jack), and they whisper a bit. He asks about her dreams, and is glad when they're good ones. Then Jack will stir (but sometimes it's Rose) and join the conversation, and after a while it stops being conversation at all and he's reminded that, even if he may have to spend his nights alone, he spends his days with them and that's pretty fantastic.