Why is my husband drilling 4 holes if various parts of our front wall????!

It all started last Wednesday. My kids and I enter our front room and smell something strange--and not very good. Alisa keeps spraying air freshner in the room. It didn't help.
Hubby came home and determined it was coming from the front vent. He cleaned out the whole thing on this side and the garage side. He found droppings of some vermin, but no mouse or rat. So he thought that maybe they crawled into some other section because of certain cracks found. That is why he started drilling. He had a handy dandy mirror to look in each section between the studs. Still no luck. He used our air classic to take away any smell. We smelled the next day. Nothing. I guess we will continue to wait and see if the smell gets worse. A friend said it could be a dead lizard. We haven't found anything. I'll keep you updated. . .