The notion of the mind being freed from the body during deep stage sleep is not only an old one but one with some science behind it. John Dunne's famous sleep studies at Oxford during the 1920s and the book that came from it—An Experiment With Time—proved that many people have precognitive dreams quite often. This should be no surprise since most of us have had a few dreams that have come true or know someone who has. The question is how? For Dunne there could be only one solution, and that involved the mind traversing serial timelines during sleep. Dunne was an engineer who designed airplanes for the first world war (mostly flown by Canadians), and one has to wonder if Marker, himself a WWII veteran, drew from Dunne's work with this story. It's a fascinating theory to say the least, and a fascinating film.