When the National Security Agency’s invincible code-breaking machine encounters a mysterious code it cannot break, the agency calls its head cryptographer, Susan Fletcher, a brilliant, beautiful mathematician. What she uncovers sends shock waves through the corridors of power. The NSA is being held hostage…not by guns or bombs but by a code so complex that if released would cripple U.S. intelligence. 

Dan Brown is the bestselling author of Digital Fortress, Deception Point, Angels and Demons, The Da Vinci Code, The Lost Symbol and most recently, Inferno. Three of his Robert Langdon novels have been adapted for the screen by Ron Howard, starring Tom Hanks. They have all been international blockbusters.