Two young men bet that their girlfriends will remain loyal. Drawn away by a trumped up call to arms and aided by Alfonso and a maid, the men return in disguise to woo the girls in an intriguing and hilarious game of fiancée swapping. The sisters initially resist the advances, but eventually break down after a series of tricks, and declare their adoration for their new loves. But sometimes a joke can go too far and the young men find their own hearts are equally susceptible to change. When the men reveal their deception, all bets are off!