Three couples, two already living in Rio; and the third, with 'the one who hates carnival', coming to visit an aunt. One of the women bets that all husbands are unfaithful. They send invitations to their husbands to the carnival ball. They find a pretext to be able to attend. They, in turn, go in disguise, just like the maid. Hence the confusion at the ball, each one dating the other's wife.