The Settembre family lives in Leopardi, a village overshadowed by Vesuvius. The small villa is inhabited by father, mother, twenty-six-year-old son Cesare, teenaged daughter Paola and their tortoise Eva.
They often receive visits from the eldest son, who is a doctor and has a family himself, and Zietta, a lady who looks much older than her age.
Cesare is studying Law and should follow in his father's footsteps, Ermanno, who is a lawyer. Father and son are completely different from one another.
Ermanno Settembre is fond of soccer: he's the coach of a local team and watches every single World Cup match. Cesare doesn't drink coffee and doesn't care at all about his father's favourite sport. One day, on the eve of his final university exam, Cesare has a mental block. An unknown pain keeps him in bed or only allows him to walk around the house lazily, in his pyjama. His friend Antonio is a practical young man and incites him to carry on - the two of them study together - but to no avail.
Ermanno is annoyed at Cesare's strange confusion, while his wife Giovanna - a distracted and anxious woman - divides her attention between her son and a gigantic, monstrous plant Cesare keeps in his bedroom. Cesare's sister Paola, meanwhile, keeps hanging out with her best friend - Antonio's sister - and creating troubles.
The Settembres' find themselves in an unexpectedly chaotic situation. Mount Vesuvius observes them in silence, changing colour by the effect of daylight and reflecting the family's moods: gray, red, yellow, blue...
One day, Antonio pays a visit to Cesare accompanied by his long-term girlfriend Milena. Cesare looks at her and, as if he seeing her for the first time in his life, he falls desperately in love with her. At first the girl is taken by surprise, then she becomes curious and, finally, definitely fascinated.
Antonio will soon discover a letter written by Cesare in one of Milena's books and tragedy breaks out: Milena is shaken deeply as she feels divided between Antonio's practical and safe approach to life and Cesare's poignant emotions which make her happy - but also quite scared.
The precarious balance of the Settembres' is now shattered and Cesare seems finished. But a strong wind starts to blow...