Ken confirmed that we have raccoon's now also visiting our yard at night, so I baited the cat food with marshmallows (a favorite treat, I know from experience in Lunenburg). Little buggers managed to drop in, snag the treats & leave before I could get back downstairs and photograph them! The clear evidence of their visit took the blame away from the prevalent possums!
So...
I'm now armed with that "baby monitor" I wanted... It's fun listening to the night sounds, but I'm still waiting...