Mary Llewellyn is a young, Welsh woman who was orphaned as a small child. Mary grew up at the home of a married cousin, a place where she was an unwanted burden. When World War I is in full swing, Mary joins the Breakspeare Unit of the French Army Ambulance Corps. It is here that Mary becomes an apprentice to Stephen Gordon. Stephen cares a great deal for Mary. After the war has ended, Stephen promises to always care for Mary. They go on a trip together in order to help Mary recover her strength after the stress of the war. During this trip, Stephen attempts to ignore her love for Mary, but Mary eventually convinces her that she understands the dangers of their love and wants to indulge it anyway.