France in the summer of 1918. A most insidious killer, the influenza virus, adds to Bess Crawford’s problems as she descends even further into war’s chaos and the battlefield’s wounded. While copious amounts of disinfectant fail to shed the smell of the dying, the corpse of Vincent Carson shows none of the darkening skin typical of the Spanish flu victim.

A lieutenant in Bess’s father’s old regiment who had just been promoted to major, Carson is found with his neck brutally broken with no hope of proving how he died. The perpetrator could be anyone: an orderly, a canteen worker, one of the ambulance drivers. The dead man’s face is deeply etched by his years in the trenches, and the dark, sleep deprived circles beneath his eyes are a powerful symbol of too many horrors witnessed.

Bess’s father, Colonel Crawford, has thus far avoided any discussion of his daughter’s time on the Front. He does assert his authority when, filled with concern, he arranges for her to be posted closer to home at Longleigh House, a private aid clinic in Somerset. As long as the war lasts, Bess wants to serve the men fighting and dying in the trenches. Furious with her mother, her father, and her beloved Simon Brandon, Bess’s life is threatened when she realizes that she was not only the last to see Major’s body but she could also have seen the man who killed him.

Melding the Somerset countryside to France's Western Front, Todd immerses his feisty heroine in the lessons of war while one Welsh farmer’s family must learn to cope with a painful rift. A serving officer all his life, Colonel Crawford understands the importance of duty. On his orders, Bess is hurriedly sent back to the Front, but she's unsure how to handle the fallout from Major Carson’s death. She must make the best of it and do what she does well--help to save lives--while the compatriot American soldier Thomas Barclay is sent by her father to keep an eye on her.

Those unfamiliar with previous Bess Crawford titles need to know that An Unmarked Grave stands on its own as a mystery. Readers with vivid memories of what happened to Bess in A Bitter Truth will notice several points of reference and an allusion to a pivotal character that appears in Todd’s Inspector Rutledge series. While there’s less a sense of suspense here than in the other titles, and the plot falls apart a bit when Bess is forced back to Somerset, the identity of the killer works to encourage empathy between Bess, Simon, and Barclay and to ultimately craft a story with an exciting, action-fueled ending.

From torn, mutilated bodies coming back from No Man’s Land, to the chaos of the forward aid stations, to the blood-soaked hospitals just behind the front lines, there’s an awful amount of increasingly grotesque and horrific description--all part of the high cost of war. Having a girl like the courageous, indomitable Bess helping out is a major plus for the Allied war effort, even when she's too reluctant to face her own mortality.

Todd is largely successful in relying on genre material, which allows him to expand on his major theme: the call of duty for people in a world of divided loyalties. The author's impressive prose beautifully evokes the Somerset countryside and the danger and despair of France, where Bess must constantly adapt and accept to new circumstances in order to survive.