Illegal substances
When the cops entered the house, they found in a hidden room deep in the basement a pile of illegal substances and a laboratory for making them. This, as you all know, was a serious crime and the cops were all over the house when the neighbor finally arrived back home.
He was quickly arrested and taken to jail to await a court hearing. But the evidence was right there in his home and there was no way he was getting out of prison any time soon. It looked like the suspicious neighbor was finally dealt with. But there was more to come for the family.