>> reporter: but police weren't so sure. they seemed intent on peeling away the veneer of the peterson's marriage. what was going on behind the closed doors in the mansion on cedar street? >> they were asking me questions about kathleen and michael's relationship. and if i knew of anything. i thought they were happily married. she was very much in love with him. >> reporter: but the detectives were beginning to believe the perfect marriage was anything but. >> despite that gore journalists house -- gorgeous house, perhaps they weren't rolling in the dow. >> i sensed the stress. i sensed that. >> and what the autopsy revealed. >> that one picture, that was it.