An American woman with a British husband fights to keep her family together through two world wars.

As she prepares for an influx of wounded soldiers at a London military hospital, American-born Red Cross volunteer Lady Susan Ashwood worries about her son John, who is fighting overseas, and fondly recalls her arrival in England many years before: In April 1914, Susan and her father, Hiram Porter Dunn, a small-town newspaper publisher from Rhode Island, arrive in London for a two-week vacation. Hiram detests everything English, especially the rainy weather, which quickly aggravates his lumbago and keeps him in his boardinghouse bed. On their last day in London, Col. Walter Forsythe, an elderly boardinghouse resident, invites Susan to accompany him to a ball hosted by the Duke and Duchess of Waverly, and she eagerly accepts. At the ball, the colonel tricks young Sir John Ashwood into dancing with Susan by leading him to believe she is his friend's Australian cousin, whom John has been asked to entertain. John is immediately taken with the down-to-earth Susan and spends a long, romantic evening with her. Just before parting, John begs Susan to stay in England, but she tearfully insists that she has to leave with her father. The next morning, however, John shows up at the boardinghouse and announces that his mother, Lady Jean, has invited both Susan and Hiram to their country manor. After much cajoling, Hiram finally gives Susan permission to stay in England without him, and she is whisked away to the country. Although they give Susan a warm welcome, John's family, including his brother Reggie, is unsure about her relationship with John and one night invite his childhood sweetheart, Helen Hampton, who is still in love with him, to dinner. John, however, is sure about his feelings for Susan and proposes, but she is too stunned to give an immediate answer. Susan then receives a telegram from her father, pleading with her to come home, and when John's family makes seemingly anti-American comments in front of her, she explodes in anger. Although Lady Jean apologizes and assures her that the English are reserved by nature, Susan prepares to sail home, convinced that she is too "American" for John. As she is about to board the ship, however, John appears and talks her into marrying him. In the midst of their honeymoon, war breaks out, and John, who, following family tradition is an Army officer, is sent off to fight. After three years of separation, Susan and Lady Jean learn that the government has arranged for soldiers' wives to be reunited with their husbands for a brief leave in France. Their joy is shortlived, however, when a telegram announcing Reggie's death in battle also arrives. At an elegant resort in coastal France, Susan and the war-weary John relish every moment of their reunion. A year later, Susan, who now lives in London, watches hopefully with her newborn son, John Ashwood II, as American troops march through the streets. Just before peace is declared, however, John is killed in action, and Susan is devastated. Lady Jean finally brings Susan out of her embittered grief by impressing on her that John sacrificed his life in order to assure his son a peaceful future. Many years later, Susan and Hiram, who now lives at the Ashwood manor, become concerned when they hear German acquaintances of young John predicting that Germany will soon "finish" the business of the previous war. Sure that another war is coming, Hiram convinces Susan to return to America with John, but while they are on the train to the coast, John, who takes seriously his duties as master of the manor, persuades her to stay in England, his home. When war finally breaks out, both John and his childhood sweetheart, farmer's daughter Betsy Kenney, go to the front. Back at the hospital, Susan's reveries are interrupted by the arrival of the wounded soldiers. As she had feared, John is among the injured and has only a few hours to live. When she sees American troops outside, marching side by side with English soldiers, however, she assures John that his sacrifice, like that of his father, will not be in vain.