Greta Garbo may be the name that draws people in – and she delivers – but I feel this film truly hinges on Melvyn Douglas’s performance as the calculating "Leon." He's the partner of the exiled Imperial Grand Duchess "Swana" (Ina Claire), residing in Paris. Because the Soviet Union is struggling financially, three officials arrive to sell her valuable jewelry. “Leon” recognizes an opportunity and obtains a court order delaying the sale, prompting Moscow to dispatch their top agent (Garbo) to handle things. She’s a straightforward communist, but hadn't anticipated the charismatic Frenchman who intends to disrupt her plans. What follows is a wonderfully amusing story that pokes fun at the authorities in both countries, the often absurd nature of beliefs, and imperfect, eccentric people. There’s a strong connection between all involved – primarily revolving around Douglas, along with his companions "Buljanoff" (Felix Bressart), "Kopalski" (Alexander Granach) and "Iranoff" (Sig Rumann) - who simply desire to run a restaurant somewhere – contributing a pleasant element of comic relief. As is typical with Bergman and Dietrich, the camera clearly adores Garbo; even her smallest expressions convey volumes. With a leading man who’s engaging and self-assured, and an enjoyable plot throughout, this makes for a thoroughly entertaining experience.

Source on TMDB