I Am a Thief (1934)

Diamond thieves seem to abound in "I Am A Thief," a 1934 film starring Mary Astor and Ricardo Cortez. Cortez buys the famous "Karenina diamonds" at auction, winning them from Astor. The two wind up on the Istanbul Express, where Cortez is hounded by an American who insists on buying the jewels from him. The story continues with murder, secret identities, mysterious telegrams, a paste copy of the jewels, and the jewels themselves.

Fast-moving story, like the train the characters ride, as the jewels change hands and different people are implicated.

Astor is radiantly beautiful and charming in the role of a flirt who has another agenda, and Cortez is elegant and suspect both.

Short at 1 hour plus, it's a delightful film.