"Been playing some chess with my husband recently", my friend Megan began, as we sat with our drinks in Coffee Monarchy.
"How'd you get on?" I asked.
"Didn't get off to a good start, I'm afraid. In our first game, he managed to beat me in only seven moves. I've still got the moves here, for what it's worth."
Megan put her big shoulder-bag on her lap and brought out a scrap of paper from it, but just as she put it out on the table for me, she knocked her coffee over. Several tissues later we'd cleaned up the spill as well as we could. But that scrap of paper was in a sorry state, and the ink had run. Now the only bit I could make out was the very last move:
K x b7#
Now, given that this was the winner's seventh move, what were the moves that led up to this victory?
This is an entry in Fortnightly Topic Challenge #40: Retrograde Analysis.