Woman of Mystery, The by Maurice Leblanc (1864 - 1941)

In 1898, a young boy watches in horror as his father is stabbed to death by a mysterious woman wearing a black lace scarf and an ornate brooch, Years later, when he arrives with his new bride at the chateau that was part of her dowry, he sees in a portrait the face of his father's murderer, wearing the same black lace and brooch -- his wife's late mother. Then he himself is attacked by a man resembling that same woman. Torn between love and repulsion for his bride, and plagued by self doubt, he answers the call to arms as world war begins. And in that war lies the answer to questions that have tormented him since the night of the original murder. - Summary by Jacquerie