After a big car accident, caused by his brother Valerio, Antonio is mentally-ill, fallen to a childlike regression. They live together in Trieste. Valerio is totally absorbed by his job and by looking after Antonio that call him Papà (Daddy). One day Valerio decide to have a trip on a house-boat with Marianna, his fiancée, and they bring Antonio with them. Antonio unexpectedly drives the boat far away till it gets stuck on a sandbank. Valerio leaves his brother and Marianna alone on the boat and goes searching for help. A storm obliges the two to spend a night together on an island. During that night Marianna discovers, step by step, the poetic and childish world of Antonio, starting to appreciate the different resources of mentally handicapped persons. Valerio will finally arrive with help.