Greg says that in a house of its era, the pipes are probably two-inch cast iron and concurs that the pipe is probably blocked. He also says there's usually an access point for clearing out the trap -- at least, I think that's what he said. He seems reasonably confident he'll be able to deal with it.

He's also bringing over a box fan for the wet carpet. I don't think it's soggy enough this time for a shop vac to be of much use.