Autumn 1915. The First World War is raging across Europe. Woodrow Wilson has kept Americans out of the trenches, although that hasn't stopped young men and women from crossing the Atlantic to volunteer at the front. Christopher Marlowe 'Kit' Cobb, a Chicago reporter and undercover agent for the US government is in Paris when he meets an enigmatic nurse called Louise. Officially in the city for a story about American ambulance drivers, Cobb is grateful for the opportunity to get to know her but soon his intelligence handler, James Polk Trask, extends his mission.