Smells Like Repairs - A foul odour came from the bathroom and after a day of investigating other areas (electrical, chimney stack) we looked at the sink. Our sink stopper had collected a lot of unpleasantness and was the source of the acetone smell.
I cleaned the stopper and decided to clean out the P-trap too. While unscrewing the plastic lock broke and I need to replace it. Unfortunately the elbow leading away from the sink isn't compatible with newer P-traps so after a hacksaw and two trips to Home Depot we have a functioning sink and the smell is gone.