This tale centers on a government agency (NSA - National Security Agency) which deciphers encryped computer codes with the aid of a master computer and program in order to thwart terrorism, drug cartels and the like. When the program encounters a code that it cannot break, it's a fast-paced trail of clues as to who has created this unbreakable code, and why that will keep Dan Brown fans turning the pages until they reach the end. Hats off to Dan Brown for another wonderfully entertaining read.