KGB agent Major Valeri Petrofsky has been reassigned at the request of the KGB Chairman for a secret mission wherein he is sent to England to establish a residence near an American military base and receive various items from couriers from the USSR. John Preston is the top British spy catcher, currently at odds with his superior because he doesn't lick his boots. After he conducts an operation without his superior's permission caused his superior some embarrassment, he is reassigned to the menial task of overseeing airports and ports. One day one the couriers Petrofsky was expecting comes off a freighter has an accident which leaves him dead. Preston is informed by the pathologist that the man is not a seaman so Preston goes through his things and finds that he was carrying something which he is told is an atomic bomb component. Preston now suspects that someone is bringing in parts for an atomic bomb, his superior doesn't want to let Preston be proven right so he doesn't authorize ...