Venial Sin (1974)

In Versillia's sandy beaches during the summer of 1956, a gawky adolescent, Sandro, spends his vacation by the sea, along with his family and the intriguingly beautiful Laura, wife of Sandro's older brother, Renzo. Under those circumstances, strange as it may seem, at first, Sandro seems annoyed by Laura's presence, however, little by little, as the two of them spend more and more time together at the beach, something will ignite a spark of interest in his sister-in-law. Sandro is determined to get what he wants, nevertheless, is Laura willing to give in?