In the opening scene of Back to the Future, a clipping from 1962 is hanging on the wall of Doc Brown's garage lab, with the headline “Brown Mansion Destroyed”.
Despite the producers believing that this plot point was important enough to introduce, none of the three movies ever adress this story beyond the fact that the mansion no longer exists in 1985.
It clearly wasn't set on fire by lightning the night in 1955 when Marty went back to the present.
So what is the story with the fire in Doc Brown's house?