Pierre Martel (Jean-Claude Pascal)is a brilliant lawyer in Paris who has fallen in love with a ravishing Italian girl, Sylvia Sorrego (Gina Lollolbrigida)and they take up housekeeping on a luxurious scale beyond his means, and Pierre commits a few irregularities and is asked to resign the Bar Association. He heads for Algeria and tells Sylvia to sell everything they own and join him there.
Sylvia is a no-show and Pierre, broke, with a dishonored name and having lost the woman he loves, dons the hair-shirt he wears the rest of the film and becomes a human wreck. What's a poor guy to do in such a situation? Well, Joe Palooka, in a similar situation back in the mid-30's joined the Foreign Legion (and Anne Howe was no Gina Lollobrigida), so Pierre does likewise.
Pierre and his friends Mario (Raymond Pellegrin) and Fred (Peter van Eyck)engage in a bit of globe-hopping warfare for the next four years and are sent back to the camp in Algeria. There, they discover a house/castle near the camp called "The Last Stop" run by Madame Blanche (Arletty), who spends most of her time reading playing cards and she is either reading from a short deck or Pierre is just a hard-luck guy as everything she turns up for him reads D-O-O-M in capital letters, or signs or pictures, or whatever is on the cards she reads.
When she isn't reading cards, Madame Blanche runs a few prostitutes on the side to keep her homestead going and arranges for three ladies of the evening to spend a night in town dining, dancing and whatever else may come up with Fred, Mario and Pierre, who haven't been to town in four years. But Pierre opts out and stays at "The Last Stop" to get drunk.
Back in town, one of the hired-hand girls turns out to be Helena (Gina Lollobrigida), who is a dead ringer for Sylvia from Paris. She may be Sylvia for all we know, although Sylvia was brilliant and spiritual while Helena is quiet and seductive---it says here---but the other attributes are the same and Viva Le Attributes. Fred and Mario toss a coin for her and Fred wins while Mario sulks in a corner wondering why he didn't insist on playing two-out-of-three, or twenty-six out of fifty-one if needed. Mario turns out later to be a sore loser.
Meanwhile, back at "The Last Stop", Madame Blanche has whipped out her doom deck and tells Pierre that he will again find the girl he loves, he will be happy with her, he will kill a friend because of her and finally lose her again. (If that's a dreaded SPOILER, tough. Blame Madame Blanche. Besides Blanche's short deck missed a couple of fill-in cards.)
Pierre finally meets Helena, spends the night with her and is convinced she is Sylvia, especially after Helena tells him she had an accident and is suffering from amnesia. Which isn't anything compared to the torment poor Pierre is suffering wondering how splendid Sylvia could have become a soldier's harlot. Helena insists that her amnesia is not such that it keeps her from knowing she isn't and never was Sylvia but Pierre isn't convinced.
But he takes Helena away from good old Fred, who doesn't even get a coin toss, but Mario is still sulking around. Plus there are still lots of unanswered questions; Is Helena really Sylvia? If not, will the real Sylvia make an appearance? Who is Pierre going to kill, Mario or Fred...or both directly and indirectly? Has Madame Blanche been playing with a full deck? Is there no end to the ability of French writers to stretch the boundaries of coincidence?
The answer to the last question is No. (Oh, is that a possible SPOILER?)