Cam Jansen and the Mystery of the Stolen Diamonds — David A. Adler

When a jewelry store is robbed, fifth-grader Jennifer Jansen knows she has to act fast. Nicknamed "The Camera" because of her photographic memory, Cam takes special care to remember what each person looks like as they leave the store. The police are baffled when witnesses say they have caught the wrong man. Cam and her friend Eric want to help, but can they catch the thieves when even the police are in the dark?