A KGB agent is sent to England to receive secret items from the USSR, while a top British spy catcher is reassigned to oversee airports and ports after disobeying orders. When a courier's death leads to the discovery of an atomic bomb component, the spy catcher becomes suspicious of a plot to smuggle parts for a nuclear bomb, despite his superior's disinterest.

The Fourth Protocol
A British agent foils a Russian plot to detonate a nuclear bomb near an American base in the UK, saving the strong alliance between the two nations from destruction.