Preston Clearwater has been a criminal since stealing two chain saws and 1600 pairs of aviator sunglasses from the Army during the Second World War. Back on the road in post-war North Carolina, a member of a car-theft ring, he picks up hitch-hiking Henry Dampier, an innocent nineteen-year-old Bible salesman. Clearwater immediately recognizes Henry as just the associate he needs - one who will believe Clearwater is working as an F.B.I. spy; one who will drive the cars Clearwater steals as Clearwater follows along in another car at a safe distance. Henry joyfully sees a chance to lead a dual life as Bible salesman and a G-man.
During his hilarious and scary adventures we learn of Henry's fundamentalist youth, an upbringing that doesn't prepare him for his new life. As he falls in love and questions his religious training, Henry begins to see he's being used - that the fun and games are over, that he is on his own in a way he never imagined.