Murder mystery with a sweaty backdrop. Off Limits (AKA: Saigon) is the missing Vietnam film, a film I feel not many have actually seen since I never see it mentioned on the message boards out there in net land. While I have certainly never heard it spoken about when talk of Vietnam films crops up. The film is in essence a who done it police drama, two cops on the streets of Saigon during the war are searching for a high ranking officer who is, erm, offing prostitutes. It is the backdrop of the war that gives the film added substance and lifts it way above average, because we see not only the…