Synopsis

Once Upon a Mattress takes place in a fictional medieval kingdom ruled by the devious Queen Aggravaine and the mute King Sextimus the Silent. King Sextimus suffers from a curse that can only be reversed "when the mouse devours the hawk". As the show opens, the populace of the castle complains about an unjust law levied by Queen Aggravaine. The law states that no one may wed until the Prince, Dauntless the Drab, first marries. However, every petitioning princess is sent away after failing an unfair test devised by the Queen. It seems that no one is good enough to marry Prince Dauntless.

The crisis escalates when the leading knight of the realm, Sir Harry, discovers that his girlfriend, Lady Larken, is pregnant. Facing great embarrassment and loss of his station, Sir Harry embarks on a quest to find the last princess in the realm. He soon returns with Princess Winnifred the Woebegone, a brash, unrefined, and muscular princess from the marshlands. She immediately charms Dauntless and most of the townspeople. However, she also succeeds in offending the Queen, who vows to find a way to stop her.

The Queen, assisted by her Wizard sidekick, quickly designs Winnifred's secret "test". They will place a tiny pea beneath twenty thick downy mattresses. If Winnifred is unable to sleep due to the pea, then she will be sensitive enough to marry Dauntless.

As the day of the test approaches, Dauntless and Winnifred fall in love, Harry and Larken break up (only to be later united by Winnifred), and the King, Jester and Minstrel trick the Wizard into telling them of the test...