This is the film l relate to about when l think about adaptations of the book (by P. C. Wren). It stars Gary Cooper, Ray Milland and Robert Preston, and is obviously in black and white. It's slightly stilted, and pretty upper class, but that is the point of the film, ie 'doing what is right'. It is confusing at first, when the French Foreign Legion reach the fort to find everyone dead, but it has a good twist at the end, both with the fort (and what happened there) and the missing jewel. A fine way to spend a couple of hours on a miserable day.