In Victorian England, handsome Brook Edgerton is deeply in love with his young wife, Harriet. They live on a country estate in Leicestershire. Felicity, an attractive young widow living nearby, becomes Harriet's best friend giving support when Harriet fails to carry a baby full term. On the ferry to Ireland Harriet meets a young mother, a destitute woman with a number of hungry children including a two week old baby. When they reach Ireland, the woman disappears, leaving the baby. Harriet, full of conflicting emotions, passes the baby off as hers and Brook's. When Brook realises that the baby isn't his, Felicity seizes the chance to widen the rift between the married couple and tries to win Brook's heart. But how stable is Felicity's mental health and how safe is Harriet?