Dog smells OK. But a skunk burrowed his way from behind the house into the crawl space (footer is way too shallow, thanks to the "builder" who hacked this place together).
I suspect a possum found the burrow and had a disagreement with the skunk, because around 6 am today, the stench suddenly returned, stronger than ever.
Sigh.

The crawl space is so low that I can't get in it (and don't want to, in case I come face-to-face, or worse yet, face-to-butt, with a skunk!)
And it's impossible to completely block off from the half-basement due to the hack work where the ducts come through.

This article looks promising. https://www.instructables.com/id/How-to-Move-a-Skunk-Out-From-Under-Your-House/
My ex also trapped and relocated a skunk, and the mothballs kept it from coming back. Going to buy a box tomorrow!
I may leave the basement hatch open, and block the burrow with rocks, so they'll exit via the basement.

Right now I have the basement exhaust fan running (although I can't run the heat with a vacuum in the basement...)
The joys of country home ownership