A lunatic is on the loose as a salesman. Steven Slade (Simon Ward) picks up a young lady, Belle Adams, (Hayley Mills) in a blue Austin Maxi car after she is nearly raped by a lorry driver.
Adams wishes to catch a train at a nearby station and Slade in wishing to take her there (really wishing to exploit her) lies about delays in her train as a way of keeping her with him.
With roadblocks in the area and Slade not being too forthcoming on his own background, the trip sharply descends into a case of what are they both hiding. This is never fully revealed.
On waking the next morning Slade loses Adams and hurries off to find her, where she misses him and catches a lift from aging Malcolm Roberts (Sterling Hayden). Later Roberts discovers Adams past and the truth of the film has yet to be uncovered.