In the 1960s, Evelyne, a 14-year-old teenager, reluctantly becomes her mother's confidante, who uses her as an excuse for romantic encounters with a work colleague. Evelyne finds this secret very difficult because she loves her father and her 12-year-old younger sister. One day, her mother leaves her husband and her two daughters. Evelyne, feeling guilty, tries to convince her to return home.

This sexy and very entertaining musical comedy shows the ups and downs of engaging in a 'ménage à trois'. When Vincent and Nicholas, a very much integrated and respected long-time couple, suddenly decide to live together with young Gabriel, they must confront the moral disapproval of their gay friends, a jealous sister, and practicalities like how to find a bed that's big enough. Filmed against a stunning Paris as backdrop, this all-out song and dance extravaganza almost explodes on-screen in a very French 'Joie de vivre'.