Lady Amelia knows that it is her duty to provide a son and heir for her husband, the Duke of Hertfordshire. But she has only produced daughters and the Duke has threatened to find another woman who can give him a son.

Pregnant again and desperate to save her marriage, Lady Amelia persuades the local midwife, Bethany Wells, to help her by finding another woman’s baby. If her fifth child is a daughter, she will substitute the other woman’s baby for her own if it’s a son. Uneasy with the arrangement, Bethany agrees.

The other woman, a maid in the Hertfordshire castle, gives birth to a son and dies. Lady Amelia names her daughter Felicity and gives her up to Bethany, who agrees to raise her as her own.

Years later, Lord George, the substitute baby who has been raised as the Duke’s heir, meets a woman who looks exactly like his four sisters. The past comes back to Lady Amelia when a letter that Bethany wrote to Felicity before her death three years before reveals the truth about the night when two babies were switched at birth.

It’s up to the adult Felicity and George, in the face of family disapproval and potential scandal, to decide whether they dare to love.