So, first of all, I just want to point out with pride that I managed to add this edition of the book to the database.
We have the lovely, innocent young woman. We have the handsome, stalwart, reticent hero. We have the exotic international setting - in this case, Capetown, South Africa. We have a missing jewel. We have the heroine flashing memories of blue fire and a mysterious sense of dread! And, we have a suitably sinister fellow wandering about interfering.
Must be a mid-20th century gothic romance.