Summer Affair (1971)

Lisa, a fifteen-year-old daughter of a wealthy industrialist, falls in love with Robert, a young hippie, slightly older than her. Their feeling is very strong, and the two decide to take a little holiday in Ponza aboard the girl's father's sailboat. During the journey, however, they are forced to land on a deserted island, because of a shipwreck. Meanwhile, the police - alerted by Lisa's parents - is convinced that the girl was kidnapped by a maniac.