In 1924 MI6 is handed a gift. An expatriate Englishman born of Russian parents is working deep inside the Russian Foreign Ministry in Moscow. He is angered that the Communists have emerged from the 1917 Revolution as the ruling faction, virtually bringing his career to an end. He must do something to ensure the government's hold on power is not long lasting. He contacts the British and offers his services.
Agent Willy Mudskipper has been assigned the task of recruiting someone to act as a liaison between the mole and his handlers. Enter Sergei Koslov, a Russian sable breeder, who makes regular sales sorties to Europe and England. Sergei too is opposed to the Communist takeover and is anxious to assist in any effort to bring the Leninists down. The plot thickens as Willy unexpectedly becomes romantically involved; pelts stolen from Sergei are already being shipped to London and a double agent is uncovered.