It is the mid-1970s, the height of the Cold War. Charles Thoroughgood, recently discharged from military service, begins, rather comically, his training at MI6. But on one of his first real assignments, the charming but inexpert spook learns from a former Cambridge classmate a secret that threatens to end his career just as it begins: Charles's deceased father, a decorated military hero, is suspected of having worked for the KGB. As Charles struggles to uncover the truth, ultimately forced to choose between honoring his father and the inexorable code of the Secret Service, he is drawn deeper and deeper into the vortex of the international intelligence machinery - far deeper than any veteran spy, much less a novice, could ever imagine.