"Right, that's going to the top of my list of things to do. I find it odd that chains aren't part of the package, when you've become a ghost." Because, well, the Doctor doesn't think it's all that likely that chains are just lying around here. Coils of rope, maybe, but that's not really going to help.

But then his expression falls a bit when Martha turns serious again. He shakes his head and raises a hand in mild protest. "Martha, don't. There's no reason for apologizing." His getting sick and eventual death wasn't her fault, and unless he's vastly mistaken, there wasn't anything anyone could have done. Medical supplies and medications aren't in abundant supply, not around here.

"It's all right, really. Don't worry about a thing." Soon enough, he'll have finished with this ghostly business, and everything will be right as rain.