Sherman Mack, dorky ninth-grader and girl enthusiast, turns detective when his crush seems on the verge of being D-listed: If a girl’s photo appears on bathroom mirrors with a circled letter D, she’s immediately rendered invisible. These D-listed, Defiled girls roam the halls like sad ghosts. Many simply disappear. To find out who’s behind the Defilings, Sherman takes cues from his friend Vanessa’s collection of detective stories and starts sleuthing. Delightful noir motifs distinguish the tale: Sherman, like a hard-nosed private eye, stakes out and interrogates suspects; Vanessa plays Sherman’s no-nonsense sidekick—a buxom broad with arched eyebrows and curves that won’t quit. As always, Juby endows her endearing characters with quirky, comedic voices and original backgrounds. Sherman’s commitment to the Defiled girls remains believable throughout, not just a lark or ploy to get ladies. When Vanessa’s photo appears on a mirror, he knows he has to close the case to save her. Sherman’s cooking-class exam—a dinner party—brings the prime suspects and Defiled girls together for a delicious final act. (Fiction. 12 & up)