"Well, it's a mighty convincing one, if it's a simulation," Rose says, letting her hand fall back to her side.

She glances at the newcomer.

""It's s'posed to be ..."

Whoever he is, he seems so calm. Must have some experience with these things.

That's reassuring.

In fact, it's reassuring enough that Rose feels like she can tell him exactly what it is and he most likely won't look at her like she's gone daft.

"Well, it's a time machine, really. It belongs to my - my friend. The Doctor."