A randomly formed group of Italians gets involved in a crime in Monte-Carlo. Starring Alberto Sordi, Vittorio Gassman, and Nino Manfredi.

Three Roman couples take the train to Monte-Carlo: Franzetti, an unremoresful gambler, and his wife Eleonora; the Capretti hairdressers; and two poor citizens, Quirino and Giovanna Filonzi, who, after finding a dog, hope to receive a reward. But the puppy’s owner has just been murdered. The fear of being thought of as suspects leads the Filonzi couple to tell lie after lie. In fact, they tell so many lies that they end up being accused of the crime. The situation is not much better for the others: the Caprettis realise that their suitcase contains the woman’s body, while Franzetti, having cheated on his wife again, makes a false confession. Fortunately, the police manage clears them. However, on the return journey, another unsolved murder puts them in a difficult situation…