The circus has come to Prague, and Willard and Miss Mallard with it. Priceless artifacts have been stolen from museums in all the big European cities. No one can explain how the thief gets through security; no one but Miss Mallard with the help of her nephew Willard. They soon learn the thefts occurred when the circus was in town and that mechanical ducks from the Fun House actually stole the artifacts. With that mystery solved, Miss Mallard and Willard turn to the real puzzling question: who programmed the mechanical ducks? It is an answer that would baffle even the most experienced of ducktectives, but not Miss Mallard.