Eleven-year-old John Watson never expected his first friend in his new Harlem neighborhood to be Shelby Holmes, a nine-year-old, four-foot-tall supersleuth whose incredible smarts are outweighed only by her big attitude. But it turns out that solving mysteries with Shelby is just the adventure that aspiring writer John needs. On John's very first day of school in New York, Shelby deduces that their new science teacher, Mr. Crosby, is in trouble. But as Shelby and John dig deeper to expose the truth, they discover there might be someone unexpected involved . . . Someone determined to outsmart Shelby Holmes. Can Shelby and John uncover the truth before the case goes from puzzling to downright dangerous?