When the National Security Agency's invincible code-breaking machine encounters a a mysterious code it cannot break, the agency calls in its head cryptographcr. Susan Fletclicr,a brilliant, beautiful mathcian,What she uncovers sends shock waves through the corridors oF power. The NSA is being held hostagc -- not by guns or bombs, but by a code so complex that releascd would cripple U.S. intelligcnce.