A Bride for Christmas, Unsuitable Brides, Bk 1.
When he finds a mysterious girl who has lost her memory, the Duke of Whitney takes her into his home. When he finds out who she is and why she was running from her uncle he vows to protect her. When Emily and the Whitney diamonds disappear, he is determined to find her and bring her to justice. Is she a diamond thief, or did she steal his heart?