1914: As the First World War erupts across Europe, Sylvie Montague defies convention to serve as a surgeon on the Western Front. Haunted by a traumatic incident in the past, she throws herself into her work, determined to save every life she can while honoring a vow she made to herself: to never again operate on someone she loves.

Amid the chaos of war, she forms an unexpected bond with the charismatic and renowned surgeon Alistair McTavish. But on the front line, where every day could be the last, there is little room for love. Fearing the consequences, both deny their growing feelings and try to keep each other at arm's length.

When a government decree threatens to remove the women in her unit from the battlefield, Sylvie returns to England to fight for their future. There, she is forced to confront the life and family she left behind – and the unresolved feelings for her childhood sweetheart, Tristan Grey.

Over the following three years, Sylvie, Alistair and Tristan’s lives become intertwined, as Sylvie has to watch the physical and mental horrors that the war has inflicted upon the men she loves. Then Sylvie’s faced with the decision to break her vow or risk losing another person she cares about. Will the cruel hand of fate steal her chance for true love?