Synopsis
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.
Dorothy Millington manages a fur shop in London's west end. She has dreamt of having a shop of her own since she first started in the fur business, but her ego and ambition get her into big trouble.
Willy arranges a surreptitious meeting with Dorothy. The plan is to beguile her and then play on her patriotism. MI6 needs a London furrier to receive shipments directly from Sergei's ranch. The shipments will be used to get information and various other items the mole has stolen, out of Russia. Willy unexpectedly becomes romantically involved with Dorothy.
Dorothy's guv, Moses Blackburn, and Sergei's foreman, Stanas Rocheski, are long lost cousins and unbeknownst to everyone, Stanas is already shipping pelts, he has stolen from Sergei, to Moses in London.
Dorothy, Sergei and Willy all go to France, and with the help of MI6, capture Stanas and Moses. Before they all leave France MI6 arrests Sergei for spying against England. We learn that Sergei and his family, have been threatened with being sent to Siberia if he doesn't agree to work as a double agent. When he is returned to England, he is overwhelmed with guilt and disgrace for having deceived Willy and for having given an entire underground cell up to the Communists, he commits suicide.
Sergei wills the money he has in England to Dorothy, hence the Unexpected Means with which to buy the fur shop.