Catsitting steps backward.

Oh, well. Letting the cats be together has ceased to be a good idea.

I think what's happened is that small is now comfortable in our place -- so, now that she feels that it's her territory, she's begun being territorial. Fortunately, our place was recently two entire apartments, which means that there is plenty of room for her to live separately for the time being. We can drop back to original cat introductions and start over.

Annoying, but, well, it happens. Cats are little balls of anger and love.