Father Brown (Chesterton's sharp-witted detective priest) and Flambeau (the reformed master-thief and Brown's constant companion) are on a little vacation in Norfolk, invited to visit the mysterious Prince Saradine. It doesn't go well. Sure, Flambeau gets some good fishing in, but there's also a duel with rapiers, a couple murders, a hanging, a case of mistaken identity, an awkward family reunion, and a gang of surly Sicilians.
