The over-heated plot of "Bonjour tristesse" is taken from a juvenile first novel by Francoise Sagan, which became a best-seller, though God knows why. For teenagers wanting to get rid of a potential step-parent it may have a certain appeal. Don't be taken in by the fact that David Niven plays the playboy father and Deborah Kerr the step-mother-in- prospect. Unfortunately, too much rests on the frail shoulders of Jean Seberg. She's beautiful and easily fulfills the image of a spoiled teenager. The problem is that she can strike poses but she can't act. Anyone who saw her as Joan of Arc in Otto Preminger's St. Joan -- Seberg's first film -- knows she was incapable at 19 of carrying a film. This movie, also by Preminger, fulfills the "promise" of the first. It was her second movie; she was now 20. What was Preminger thinking? That Niven and Kerr could compensate for Seberg's lack of acting capacity? Not a chance? Seberg's character is at the center of the story and, pretty though she is, convincing though she may be physically as a 17 year old, she can't meet the emotional demands of the role. I don't know if she ever became a successful actress in her short life because she did not have an impact on my consciousness in her later pictures. But anyone who thinks this film is better than mediocre needs a taste check. In spite of Niven and Kerr, this remains a juvenile story executed in juvenile fashion by a beautiful young girl who badly needed acting lessons.