In their second appearance, the likable ""Investigators of the Unknown"" (introduced in The Gold Dust Letters, p. 399) now include withdrawn classmate Walter Kew, while former protagonist Angela is offstage in Mexico, leaving her cat Juliette in animal-lover Poco's care. When Juliette vanishes after a nearly fatal brush with a speeding car, the three friends (with Georgina trying to overcome her normal incredulity) seek clues to her whereabouts with Waiter's Ouija board. Concluding that a cryptic message (""deadly enemy"") refers to a retired teacher now living, as caretaker, over Angela's garage, the three shadow her -- only to discover that (like Angela's dad in the first book) she's a kindly soul. The witchy manifestations that have excited their curiosity and fear all have ordinary explanations. In the end, as cats do, Juliette turns up on her own, while the mystery of Walter's parentage is left hanging as a teaser for a sequel. Newbery Honor--winner Lisle adds spark to the predictable goings-on with lively, idiosyncratic characterizations and spooky trimmings. Easy, good-quality fare.