This is way out there, and has been on my mind since the murder. I don’t think it has been mentioned. IIRC, within the week prior to the murders, some guy in the general area of the Dermond’s house, a person advertised gold for sale. Gold bars or whatever form it os sold in. The next thing in the news was the heinous double murder in the same area. Could Mr. D have sold a few gold bars and no one was aware of it? Why not? His sons didn’t know exactly every move the parents made? Perhaps the robbers came back and stole their money back or killed them at the time of purchasing the gold. This sticks in my head of is it connected? Is this the missing piece?