Istanbul (1957)

Adventurer James Brennan returns to Istanbul five years after being ejected under suspicion of diamond smuggling. In flashback, he recalls his last days there, his torrid love affair with Stephanie Bauer, the efforts of shady characters to obtain a strange ornament he received from a friend, and Stephanie's disappearance during a fire. Now that Brennan is back, Stephanie (or her double) reappears, and there's still the question of where the supposedly smuggled diamonds are...