Bob and I both bailed out of the office at 4:30 and headed home to run the hand auger in the hopes that we would not need to call a plumber. I'm not sure exactly what running the auger entailed, as there isn't room for both of us in that bathroom. But the end result is that there was a "glorp" and all the water abruptly dropped to where it was supposed to be. I'm told that a quantity of hair came back out, but not really enough to justify the problem. The glorp was brought on by the plunger though, so the real guts of the clog are probably out in the septic tank. Where they belong. There was much running of water and proper flushing of the toilet, and everything appears to be functioning as it ought. We followed up with a half a bottle of Dawn and fifteen quarts of boiling water down the shower drain. The downstairs bath has been reclaimed as a bathroom.
There is a whole lot of bleach in our future. But I think it can wait until tomorrow.
I wonder what the next adventure in home owning is going to be?