Obsession — Claire Lorrimer

In Victorian England, handsome Brook Edgerton is deeply in love with his young wife, Harriet. They live in beautiful Hunters Hall, a country estate in Leicestershire. They are a happy marriage,but Harriet is unable to produce the heir her husband, Brook, craves. She finds sympathy and friendship from Felicity Goodhall, an attractive young widow who lives nearby. Felicity becomes Harriet's best friend giving support when Harriet fails to carry her baby full term.
On the ferry to Ireland Harriet meets a young mother, a destitute woman with a number of hungry children including a newborn baby. When they reach Ireland, the woman disappears, leaving her two-week-old baby boy to Harriet. With Brook far away in Jamaica on business, Harriet's desire for a child leads her to a life-changing decision. Harriet, full of conflicting emotions, passes the baby off as hers and Brook's.
When Brook realises that the baby isn't his, their marriage is in danger of falling apart. Meanwhile Felicity has developed an obsessive passion for Brook, and seizes the chance to widen the rift between the married couple and tries to win Brook's heart. But when her seductive plan to win Brook's love are unsuccessful, she realises she has no alternative but to outline other malevolent plan to get rid of Harriet once and for all. But how stable is Felicity's mental health and how safe is Harriet?