It's lucky that seventh graders Dee and Adrienne, who are after school library volunteers and ""sort of"" cousins: have practiced their telepathy trick, sneaking each other the mystery number in the sweatband of Uncle Ray's hat. Because when Adrienne's former stepfather (a compulsive gambler) kidnaps and holds her for ransom, that's how she informs Dee of her whereabouts. Of course both Dee and Elmo, the library's shelving boy who is bugged by the girls but enamored of Miss Kitamura, his karate teacher, have to do a bit of research and some chasing around before they find Adrienne's captor. But with the fire department clearing the house on Elmo's false alarm and Elmo stopping the villain with his karate, there are no major hitches. Neatly calculated as usual, though not one of Corbett's more mystifying numbers.