Dartmoor, 1914. 24-year-old Marianne Warrington is in danger of being left on the shelf. But she has her future mapped out and it doesn't include marriage or babies. Instead, she vows to devote herself to rearing horses on her parents' farm. Then World War One breaks out and the Warringtons' peaceful existence is shattered forever. Amid the chaos, Marianne seizes her chance to prove she's more than just a spinster. When her brother leaves for the battlefield, Marianne is determined to follow. She signs up to serve as an ambulance driver in war-torn France. There, she witnesses unimaginable horrors. Yet there's one face she can't banish from her thoughts. It belongs to Major Albert Thorneycroft: a handsome and perplexing stranger who means more to Marianne than she'd care to admit. As the war rages on, a battle ensues between Marianne's head and heart, testing her resolve like never before.