Charley Wyckham and Jack Chesney pressure fellow student Fancourt Babberly to pose as Charley's Brazilian Aunt Donna Lucia. Their purpose is to have a chaperone for their amorous visits with Amy and Kitty, niece and ward of crusty Stephen Spettigue. Complications begin when Fancourt, in drag, becomes the love object of old Spettigue and Sir Francis Chesney.
Marco Polo travels from Venice to Peking, where he quickly discovers spaghetti and gunpowder and falls in love with the Emperor's daughter. The Emperor Kublai Khan is a kindly fellow, but his evil aide Ahmed wants to get rid of Kublai Khan so he can be emperor, and to get rid of Marco Polo so he can marry the princess. Ahmed sends Marco Polo to the West to fight barbarians, but...