Tune in to shortwave radio at the top of each hour and you will stumble upon a confusion of mysterious-sounding messages: voices reading random groups of numbers interspersed with noises and bizarre musical quotes.
These are the so-called "number stations". Nobody has ever admitted to broadcasting them, intelligence agencies have traditionally denied their use, and they are unlicensed. Simon Fanshawe embarks on a thrilling detective journey into the clandestine world of radio cryptography, and attempts to solve one of the most unusual broadcast mysteries. (R)