It was misleading to call it a "rescue" victim. It was my own carelessness! I was away and didn't water it well--a year or more ago, and it suffered greatly, dropped leaves, etc. But it started a comeback. Right now I suspect it needs repotting. I'll try that next.
I was hoping someone might have seen that totally black leave thing. I've never seen it before.
Picture below is a couple of years ago when it was at it's best.