The Mona Lisa has disappeared! In The Case of the Missing Mona Lisa, expert detectives Freddy and Ellie® board an airplane to Paris and find themselves in the middle of a mystery that needs to be solved. The famous Mona Lisa painting has been stolen from the Louvre Museum! Who could have done such a sneaky thing? Hidden “red reveal” clues, viewable with the included Track Tracer, allow kids to follow the clues and solve the mystery just like world-famous detectives Freddy and Ellie.