When Joe and Frank Hardy are on a field trip to the Bayport History Museum, they witness a robbery! A man dressed all in black stole an expensive painting right from under their noses and managed to get away with it. What the boys didn't realize is that the day before, the robber sent them a riddle warning them of the robbery, but they didn't open the mail until it was too late. All the evidence points to Phantom, a recently released ex-con who is known for sending riddles about his crimes. Joe and Frank are in a cat and mouse game with the robber, and are trying to stay ahead when they realize that the true prize that the thief is after is the valuable jewel the Emerald of Astara. Can the Hardy boys figure out who is behind this epic master scheme?
