In 1943, Honora Ellery-Smythe receives the telegram that signals the end of her life as a French literature teacher. Determined to make her husband's death in North Africa meaningful, Elly enlists in the Women's Auxiliary Air Force and trains as a radiographer.

During her service, her abilities are recognized, and she is recruited into the Special Operations Executive, the covert agency that sent spies and resistance trainers into occupied territories.

An Unorthodox War weaves together real events and people as Elly masters her new trade and tries to survive the dangers, betrayals, and brutality that these remarkable women faced during their short and often fatal deployments.