Two just-married Venetian gondoliers are informed by the Grand Inquisitor that one of them has just become the King of "Barataria", but only their foster mother, presently at large, knows which one. As Barataria needs a king to put down unrest in the country, they travel there to reign jointly, leaving their wives behind in Venice until the old lady can be interviewed. It turns out that the king was wed in infancy to the beautiful daughter of the Spanish Duke of Plaza Toro, and so it seems he is an unintentional bigamist. Of course, the beautiful daughter is in love with a common servant! When the young Spaniard and the two Venetian wives all show up wanting to know which of them is queen, complications arise. No worries: The true identity of the king is revealed, and all is combed out spectacularly well by the end.

synopsis taken from The Gilbert and Sullivan Archive