Georges Vallier is a famous screenwriter, author of vaudevilles. He jealously keeps the secret from the existence of his "ghostwriter" Pierre Renaud, without frustrating him. However, he invites Pierre to replace him at a cocktail given by Aldo Barazzutti, an Italian filmstar. While thinking, he is Georges Vallier, Barazzutti asks him to go with him in Tunisia for the screenwriting of his film. Taking the opportunity, Pierre Renaud tells Georges Vallier that he quits working for him and leaves with Barazzutti for Tunisia. He will later reveal the truth by telling him that he is not Georges Vallier. Pierre leaves temporarily his wife Charlotte, about to give birth, in Paris.
He ignores that Barazzutti was using this trip as a pretext to be with his mistress Valérie and Pierre has never had the occasion to reveal his real identity or be part of his project of screenwriting, where he would abandon the vaudeville for more political subjects. Having disputed with her lover and being attracted to what represents the famous Georges Vallier, Valérie takes refuge with Pierre, even if he rejects her. Barazzutti then sets his sight on Anne-Marie, a customer of the hotel married to a military. The arrival at the hotel of the real Georges Vallier messes the plans of Pierre : he has to multiply the stratagems to hide from Vallier while avoiding that he meets Barazzutti. He then discovers that the presence of Georges Vallier comes from the fact that he is the lover of Anne-Marie. It is while she both hides them in a closet that Georges Vallier finally meets Pierre.
