Direct from University, the painfully shy and reclusive George Withers is asked to join MI6 as a cryptographer.
After ten years faithful service he leaves to become editor and compiler of the crosswords of the Times and Sunday Times newspapers. Now, after thirty years of having cracked the brains of readers who struggle to complete his cryptic crosswords, an old MI6 colleague asks him to place a code within one of the Sunday Times cryptic puzzles. George is totally unaware the code is a catalyst for a number of gruesome deaths around the world.
A Serbian father of one of the victims, and ex-henchman of President Tito, discovers the puzzle maker has something to do with his son's death, and goes on the hunt.
Georges' quiet world of puzzles changes into a nightmare of being hunted through the streets of London, and a fight for his life. While on the run he tries to decipher that last fatal cryptic message he got from his friend, who has now disappeared, and solve a puzzle that will hopefully save his own life.
In trying to solve the puzzle the can of worms he opens not only brings the intelligence community to its knees, but rocks the foundations of the United Nations as an organisation and leads to its possible destruction.