In a tented field hospital on the coast of France, a team of doctors, nurses and women volunteers work together to heal the bodies and souls of men wounded in the trenches.
The hospital is a frontier: between the battlefield and home front, but also between the old rules, hierarchies, class distinctions and a new way of thinking.
In the first episode, Kitty Trevelyan tries to put the troubles of her past behind her as she joins two other girls, Flora Marshall and Rosalie Berwick, to volunteer at one of the busiest war hospitals in Northern France.
For the hospital workers, its a daily battle to patch the men up and keep the war machine churning.
Staff numbers are low and the volunteers are desperately needed, yet there are some who see these women as more of a threat than a lifeline.
Its not just the girls who are causing a stir. One particular patient is facing certain death but resisting it with all the strength he can muster.
Alongside him lies the shell-shocked form of Lance Corporal Prentiss. He may be physically unmarked but this war has damaged him badly, and the staff are at a loss as to how to treat him.
As the three volunteer nurses settle into their first day, it soon becomes clear that no training could ever have prepared them for the reality of working near the Front Line.
Before the day draws to an end, the hospital sees the arrival of Sister Joan Livesey, but it remains to be seen whether her modern approach will be welcomed...