The first picture below is an old stain on the ceiling of a client of ours. There had been a leak a year or so before we began Home Watch at this property. It had been previously "taken care of", and all that remained was the staining. I documented photos of each of these areas throughout the home on my very first visit. I refer to these each time I visit, to be sure nothing has changed. Upon one of my last visits, I noticed a dark spot (phone #2, on the right) in the middle of the previous stain that I didn't remember from before. Mind you, there is no strange odor, and no other indication of any abnormality. When I referred to my original picture, it was clear something had changed. I immediately called a remediation company I work with, and had them come out and perform a free consultation (at the homeowners permission, of course). The professional found that mold had started to grow in the attic. He said that is was less than 10 feet and could be easily remedied.
Early detection is the key! Had this continued to bloom, it could have cost the homeowner thousands.