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 for 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 a recent operation 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 has an encounter with customs which leaves him dead. Preston then goes through his things and finds that he was carrying an atomic bomb component. Preston now suspects that someone is bringing in parts for an atomic bomb, and obtains permission from an official higher than his own superior to attempt to find this person. And back in the USSR, Petrofsky's boss is so disgruntled that Petrofsky has been taken from him that he calls his old friend, the Vice-Chairman of the KGB, to find out what's going on because he believes that the Chairman wouldn't be able to do any of these things without his friend's input. But his friend is just as incredulous as he is. So he tries to find out what the Chairman is up to.