Mister Jerico (1970)

Dudley Jerico (Patrick Macnee) sets out to rob corrupt millionaire Victor Rosso (Herbert Lom), of his legendary Gemini diamond. Rosso is obsessed with obtaining the stone’s twin so Jerico obtains a perfect copy of the stone as part of his plan to swindle Rosso. But before he can fleece him a mysterious woman from Paris called Mademoiselle Claudine (Connie Stevens) appears, claiming she has the twin Gemini diamond. Rosso knows that one of them is lying, but which one..?