World War I has broken out and two Englishmen, Ivan Durward and John Trenchard, go to Russia to help on the front as medics. Durward is objective and forthright, while Trenchard is dreamy and possessing little self-esteem. Trenchard falls in love with a Russian nurse, Marie, and they become engaged. But the older and roguish Dr. Semyonov also falls in love with her, and is able to take Marie for himself.
Much of the book is related through a diary kept by Trenchard and another one by Durward. The tone of the book is very somber, even melancholy, despite the passionate love interests. The war plays a large part of the story, but it would not be fair to call it a "war novel."