Smell

My in-laws have an 05 rx330 and the other day he said he thought there might be a dead critter in the air coming into the cabin. Has anyone had that problem and is it possible for something like a small ground mole, etc to get in. Don't those cars have a filter for the cabin air? If so where would they get in? Could it be mold as we had a very humid summer and he doesn't drive the rx much at all. I had that problem with a Mustang once and I got a can of stuff to clean out the smell.