Since Topeka is a decent-sized city, I found a bike shop and bought a new spare tube. Glad to have that taken care of! I also had them check the loose spoke in the rear wheel, but it was nothing to worry about -- a normal consequence of the tight spokes on the opposite side of the rim.
I had breakfast and went shopping, then browsed around the town for a while. There wasn't much to see so I retreated to the motel room to crop photos and write. A low-key Halloween for me, and that's just fine!