Mysterious thing, time. Powerful, and when meddled with, danger...
Dumbledore: Mysterious thing, time. Powerful, and when meddled with, dangerous. Sirius Black is in the topmost cell of the dark tower. You know the laws, Miss Granger. You must not be seen, and you would do well, I feel, to return before this last chime. If not, the consequences are too ghastly to discuss. If you succeed tonight, more than one innocent life may be spared. Three turns, should do it, I think.
[He starts to exit, turns back]
Dumbledore: Oh, by the way. When in doubt, I find retracing my steps to be a wise place to begin. Good luck.
Ron: What the bloody hell was that all about?