But after a couple days, and leaving the windows open to air out, it hadn't gone away, and I went looking for the real source. Tonight, I found it. In the kitchen of all places -- I never go in there.
Apparently, a jug of drano had gotten a leak. Highly acidic goop leaked into the cabinet, then dripped out the door to pool on the counter. It was kind of pretty -- like a white, scruffy icicle of crystalized nastiness.
But aside from the fumes, it managed to eat away the paint on the countertop (revealing a lovely floral pattern) and once I scraped away the icicle-thing, there was about a cubic inch of wood missing from the cabinet, completely dissolved.
...I don't think I'm getting my deposit back.