I wrote the Prine site and asked if the LOC would sell a copy of video - they suggested we all write and ask them to do that - it's the next thing I do!!
Lake Marie is a lake near Lake Geneva - close to Chicago - where all the folks used to drive to in the Summer - before air conditioning. I would guess the song is a confluence of childhood memories there at the lake and the crime stories that were so common in Chicago in the '50's about bodies being found in the forest preserves - the traditional spot for leaving mob murder victims. Remember Jake "Greasy Thumb" Gusik and Paul "the Waiter" Ricca?
Looking forward to hearing your interview, Mike.
Chris in Da Loop