When the National Security Agency's invincible code-breaking machine encounters a mysterious code it cannot break, the agency calls in its head cryptographer, Susan Fletcher, a brilliant, beautiful mathematician. What she uncovers sends shock waves through the corridors of power.
Oliver Marks has just served ten years for the murder of one of his closest friends - a murder he may or may not have committed. On the day he's released, he's greeted by the detective who put him ...