The good news is that I have my laptop back. The power plug had come unplugged internally. (Basically, if I had an independent method of charging my battery, I could have kept going.)
Chapter 18 is maybe two or three pages away from completion. As long as there is no more bad luck, it should go up this weekend or next week.
Chapter 19 is maybe 1/4 done, while Chapters 20 & 21 are probably each about halfway done.