X is for X-ray... Dink, Josh, and Ruth Rose are having an excellent time at the Penelope Gwinn concert. But during intermission, Dink injures his arm! At the same time, the singer's diamond necklace is stolen. Could the two mishaps somehow be connected? And could Dink's X-ray be a clue? It's up to the kids to examine the evidence and find out in this exciting yet easy-to-read chapter book mystery.