Now I feel stupid

This morning the construction dudes showed up to start tearing down the wall in search of mold and mildew. The first thing Randy asked is "Could the smell be coming from the drain?" so I stuck my nose down in that nasty little hole and yup, there is a mold and mildew stench coming from there.

So the new strategy is some drain cleaning followed by a some more drain sniffing before proceeding to destruction. I'm keeping my fingers crossed that I'll get through this with a bit of egg on my face and no further construction.