A thriller for boys, with plenty of excitement but no more literary merit than any of the late afternoon radio hair-raisers. This has the double selling appeal of planes and mystery, a fast seller no doubt and not harmful unless a boy devotes too much time to it. A quick reader can gulp this type of fare and go on to better stuff. This story is laid in the unusual sandy dunes of the California-Mexico border and includes flying, patrols, picture-taking spies and all the usual melange of trickery, bravery, and fast thinking.