It turns out that Bunny's brother is a qualfied electrician, and even though he's 3,000 miles away, a few pictures and several phone calls were enough for him to walk us through replacing the problematic outlet [1]. The hardest part—kneeling on the granite gravel beneath the outlet. Ouch. But we had everything we needed. I even found a duplicate receptacle tester in my toolbox!
And now the outlet works. But I did state to Bunny that if that outlet ever gives us trouble again, I'm calling an electrician—I'm not kneeling on gravel if I can help it.