Jen doesn’t want to spend her 17th summer working at her grandmother’s bed-and-breakfast inn, but her dad says she has to. She’s just broken up with her boyfriend, though, and she finds herself becoming far too attracted to her “uncousin” Mark, her grandmother’s step-grandson. Worse, Jen’s archenemy also works at the inn, and the girl appears to be making a play for the newly fascinating Mark. The plot thickens when Grandma Kay decides to have one of her popular “mystery weekends” at the inn, but with a difference. This time Grandma Kay wants to find out what happened to Jen’s mother, who disappeared years earlier. Grandma Kay suspects murder, although Jen has been receiving gifts and letters from her mother ever since she left. Jen winds up reluctantly playing the murder victim in a game that easily could turn real. Nitz intertwines and then untangles relationships among the teens and guests, weaving a credible mystery for a wide adolescent audience. With clues and red herrings neatly scattered throughout, the book scores as a darned good little mystery. Intriguing, suspenseful fun. (Mystery. 12 & up)