Neighborhood spark plug/sleuth Hazel Green solves a double mystery, and picks up some cogent insights into her own and human nature in the process. When two prize lobsters go missing, the fishmonger Mr. Petrusca sinks into sudden, disproportionately deep depression. Determined both to finger the culprit and to bring Mr. Petrusca back to his usual bubbly self, Hazel enlists the aid of friends and begins to dig—and discovers that Mr. Petrusca’s reaction stems not from the theft, but from the fact that the thief left a note which he can’t read, never having learned how. Swearing her to secrecy, Mr. Petrusca explains how, often with the silent collusion of others, he has managed to keep his guilty secret; breaking down his resistance to change becomes Hazel’s second challenge, once she’s cleverly engineered the lobsters’ return. Hirsch leaves the day-to-day details of Hazel’s life sketchy, but he draws characters, particularly adult ones, in some (sometimes-quirky) detail, while endowing Hazel with a mix of strong-mindedness and quick wit reminiscent of a younger Sammy Keyes. (Fiction. 10-12)