This horror film is about a soldier who dies in Vietnam- or not- and how his family deals with him being dead - or not- and he could be a vampire zombie with a real individuation problem- or not
it's seriously seventies and feels like an expensive home movie that was filmed in constant "movie" darkness- think Attack of the Eye Creatures, without the loveable characters- There really aren't any famous actors except for veteran actor John Marley who was in The Godfather and Hooper- here's the trailer and the IMDB link

http://www.dailymotion.com/video/x2e7vi1_dead-of-night-1974-trailer_shortfilms
http://m.imdb.com/title/tt0068457/