Who: The 11th Doctor, Charles, and eventually Jenny. If anybody else want to wander into the TARDIS as well, you are free to do so.
What: The Doctor is lost in the TARDIS, scared and lonely, while his mind attracts Charles' enough to lure him in as well. Jenny will have to rescue them.
Where: In the Tardis, duh.
When: Backdated to the start of the event, at least for the Doctor.
The Doctor woke up alone in a strange room. Or was it strange? ... He couldn't tell. His surroundings were imposing and unfamiliar. He looked down at himself, trying to gather his thoughts.
He was dressed... well, he had no standard of comparison. It looked fine to him, and the cloth tied around his neck... that was comforting, for some reason. Good thing, too, because - come to think of it, he really doesn't know who he is. Well, that... is pretty disturbing.
All right, no good dwelling on that, now. Why does he feel so sad, though? Did something happen?
Ah, no use. He can't remember anything. "Hello? Hello, is anybody there?!" His voice echoes and disappears quickly. He would try to find an exit. That would be best.
Half an hour later, he's beginning to despair of ever finding his way out. Where was this place? Wasn't there anybody else here? Maybe... maybe he is all there is. He has some sort of concept of other people, way in the back of his mind, but they're always ephemeral and fleeting. Somehow, they never last.
He falls to the ground as a sudden and crushing wave of loneliness beyond anything he's prepared to handle sweeps over him. He thinks there must have been people here, once - otherwise why would he be so lonely now?
He curls up for a moment, trying and failing to get a hold of himself. He's wracked with loneliness and sadness, curled up and sobbing on the ground, and throughout it all he has no idea
why.