On St. Stephen's Day, King Arthur and his knights traditionally change places for one day with the court squires. During the day, one of the ""squires-for-a-day"" steals the Sword of Excalibur.

As a punishment because he rebels at working with Merlin's pigeons, Squire Brian is sent on an errand to deliver a crate of pigeons to a neighboring castle. En route, he becomes involved with a gang of thieves who stole the precious Ruby of Radnor.

King Arthur and Sir Lancelot disguise themselves as thieves in order to test the validity of a statement by Lancelot. The knight believes that the thieves of the kingdom are thieves only because they are starving.