Fabio Bonetti (Alberto Sordi) is a normal bank employee, enjoying the security of a peaceful home with a loving wife and pretty teenage daughter -- until he comes across some film surreptitiously taken by a private investigator that reveals his wife Flavia (Monica Vitti) in a whole new light. The Super-8 clips were taken by mistake -- the private eye thought he was filming the society woman who lives above the Bonetti family -- but they change Fabio completely. Each day he learns a little more -- first, he sees that his wife drinks when no one is around, secondly, he discovers that his daughter sometimes gets high on heroin, and that Flavia was able to save her from a descent into prostitution. Next, he learns that his doctor had (mistakenly, it turns out) told Flavia that Fabio only had a few months to live, and as a final blow, he sees that his wife strayed from her years of fidelity once -- and only once -- and that brings him to the brink of suicide. As time goes by, Fabio not only comes to care for his wife more deeply, he has to consider how he should bridge the gap that has grown between them -- and whether or not he should confront her with the truth.