Mary Roberts Rinehart, known for her bestselling mystery novels such as The Circular Staircase published in 1907, earned a reputation as "the American Agatha Christie" through the success of her novels. Yet Rinehart was also a WWI correspondent. After convincing her editor at The Saturday Evening Post to send her to the Belgian front, and armed with letters of introduction, her status as a well-known writer and member of the American Red...