Knight Without Armour (1937)

In the last days of Czarist Russia, Russian-speaking Briton A.J. Fothergill (Robert Donat) is enlisted by his government to go undercover as Bolshevik radical Peter Ouranoff in an attempt to gain access to the revolutionaries' inner circle. Given the task of accompanying beautiful aristocrat Alexandra Vladinoff (Marlene Dietrich) from Moscow to Petrograd to be tried for crimes against the proletariat, Peter becomes her lover and attempts to spirit her out of the war-torn country.