Bert (Robie Porter) and Taylor (Sam Waterston) are two Americans who set out for a tour of France and Italy by auto. They meet a pretty female hitchhiker named Marty (Charlotte Rampling) and agree to allow her to travel with them. They agree not to become romantically involved with Marty to insure there is no conflict. When Bert goes off with a French woman for a night of love and romance, Marty makes a move on Taylor. Keeping in mind the pact with his friend, he refuses to get involved with the woman. Bert eventually returns and forgets his promise to Taylor as he makes a pass at the willing, wanton woman. Soon Taylor is left behind to ponder his fate as the two lovers resume the proposed tour.