Join the shy but brave mouse Bernard and his glamorous partner Miss Bianca -- two tiny heroes on a great big mission to save a young girl named Penny who has sent an urgent call for help! Taking off on the wings of their trusted albatross friend Orville, Bernard and Bianca soar to the marshy swamp of Devil's Bayou. There, they find themselves on the riverboat hideout of the hilariously evil Madame Medusa, who needs Penny to retrieve the world's largest diamond! But before Bernard and Bianca can bring Penny safely home, they'll have to enlist the help of some spirited local swamp critters in order to outwit Medusa ... and outrun her pet crocodiles Nero and Brutus.
