Stop That Musketeer! +Audio

At Abby and Dean's school, there is a costume party to collect money for a history trip to France and Italy. During the party Abby discovers that the box with the money is missing. At the same time Dean sees a man in a Musketeer costume and notices that the man has the money box! Dean tries to talk to him, but the man runs away. Who is the misterious musketeer? Can Dean and Abby stop him?