He stood outside the TARDIS, staring through a window at Martha and her family, watching their faces as they spoke animatedly to one another. The part of him that was fooling himself told him she was saying her good byes, defending her reasons to leave with him as her family tried to change her mind.
The rational part of him knew that wasn't the case.
Even without hearing their words or observing what went on between them, the Doctor knew they weren't trading farewells. He could feel it, that precognition, that sort of drag that came upon him when he just knew, one way or another, that his companion would be leaving him. Call it a sixth sense, call it acute perception, call it whatever you like. He could feel it, and he felt it now.
It was only confirmed when Francine turned to look at him through the glass. It was a silent exchange of sorrys and thanks. Of good byes. He returned her sentiments with his own weighted stare, and turned to step inside the TARDIS. The ambient hum of the TARDIS was so comparably quiet to the street beyond the doors that it almost set his ears to ringing. No one asking what took him so long. No heated debate or teasing conversation between a time agent and a medical student. No accusations from a kidnapped bride or objections from an Idiot. No reassurances from a shop girl turned defender of the earth.
Alone.
He watched himself tinker with this and that, trying to ignore the inner workings of his mind. He could just pull the lever and be gone straight away. No big scene, no difficult goodbye. If he just left, just like that--if he could leave in an instant, then it didn't mean that much, right? It wouldn't hurt to have her gone, if he could so easily up and go.
Alone.
But he couldn't. Even if he somehow summed up the courage or the cowardice, it wouldn't be fair to her, especially after everything she'd done for him. So, he waited, pretending he was wrong about it all, even after she stepped inside without any of her belongings, her footsteps faltering. He threw himself into departure mode, whirling about the console like a lunatic, advertising all sorts of destination opportunities like some kind of intergalactic travel agency. Until their eyes met, and he dispensed with the self-deception.
And so it was he and Martha who traded farewells that day. He understood, he really did, and a part of him wanted a little seclusion after exposing an entire buffet of his vulnerabilities to so many people recently. When she came back a second time, and was honest with him, when he was left with the commitment of a friend and the solid weight of her mobile in his hand, he told himself he could deal with it now. It was only the melancholy separation of two friends who lived far away. Sad, but still holding promise down the road. He could deal with it easily.
He kept up that particular self-delusion for about thirty seconds after the door closed behind her, and then the weight of it returned, dragging him down once more. He was an observer, far away, watching himself play a little game. A game where it didn't matter when they left. He played along, even as he threw the lever to depart. And when the RMS Titanic crashed into his console room, no one was there to share his astonishment.
Alone.
But hopefully, not for long.