The Mare by Angharad Hampshire

In 1939, when she was just nineteen years old, Hermine Braunsteiner applied for a job in a new prison which had opened near her home. She had heard that the pay was better than working on the factory line. The prison was called Ravensbrück. A few months later, the Second World War would break like a wave across Europe. By the time it was over, she had become one of the most notoriously cruel and violent guards in the Nazi death camps. The prisoners nicknamed her the Mare - she was known for kicking her victims to death. After the war, Hermine disappeared back into civilian life. A few years later she met a US war veteran who was holidaying in Europe. He had no idea who she was. He fell in love with her, married her and brought her back to America, where she lived for years as a well-liked suburban housewife, until one day a tip-off from a Holocaust survivor sent a New York Times journalist to their door, and the questions started.