Ugh, thanks. It looks like three out of the four were either templates or otherwise not used - content/blog is the only one that is: I deleted the other three and re-built the site and it loads correctly. But, that darned, extra post, which isn't in that one directory that I kept, still renders. I did look for any rendered HTML files (in that directory - and with the words contained in the title of the post, in case they were hiding anywhere else), but the darned file persists. How can I clear my cache?
Well, it's a little hacky, but I found it in the index.html file, and deleted it there - as well as the directory in the directory with the rendered files that remained there - and that seemed to do the trick. Thanks for suggesting I simplify things by finding which directories contained posts: That helped me to try to understand the structure of the site a bit better and got me heading in the right direction. Thanks again!