Well, if that isn't just a kick to the chest. Well done, in so few words, too. The tension, both the good and the bad, it was tangible.
Oh, and this:
Sirius smiled and dropped onto the old, red leather coach, familiar in the way all of the house is, his home before Azkaban, but alien too, in the way that he had expected nothing to change. Not even Remus.
That was a perfect description, I feel, of how it must have been.

Wonderful job.