Adventures of Tartu, The (aka Sabotage Agent) (1943)
Starring: Robert Donat, Valerie Hobson
Plot: Stevenson, a British soldier fluent in Rumanian and German, goes undercover to sabotage a German poison-gas factory. He turns himself into Jan Tartu, a member of the Rumanian Iron Guard. But when his contacts are destroyed, his cover may get him killed by the very underground he needs to succeed.