The Return of Sophie Lang

In order to give up her life of crime and go straight, renowned jewel thief Sophie Lang fakes her own death and retires to London. She soon finds a job as a companion to a wealthy old lady who is also a jewel collector. One day her employer decides to take an ocean trip to the US, taking Sophie with her. She also takes along a $200,000 diamond, which she locks up in the ship's safe. Of course, the diamond is soon stolen from the safe.