The San Francisco-based millionaire industrialist Walter Williams (Brian Donlevy) has a young wife, Irene (Helen Walker), who is trying to kill him with the help of her young lover, Jim Torrence (Tony Barrett).
After Walter and Irene make plans to drive to Lake Tahoe, Irene feigns illness and asks Walter to instead give Torrence, who is pretending to be Irene's "cousin" from Illinois, a lift to Denver, allowing Torrence a chance to murder Walter en route.
