Michael Hurst is obsessed with the ancient amulet of Hurst family lore and is determined to find it after all these years. But during his search, Michael disappears, and his younger brothers set out to find him, leaving their sister Mary at home waiting for word from Michael. So, when a message arrives that William is being held prisoner and will be released only if his family returns a certain artefact, a black onyx box covered in runes, Mary sets out to retrieve the item from William's friend and fellow antiquarian, Angus Erskine.

When she arrives in Scotland though, nothing is as she expects. The keeper of the box, the sexy-as-sin Earl of Mar, believes her to be an impostor, sent to seduce him into giving it to her. But Mary refuses to leave until confirmation of her story arrives from a mutual friend, and in the meantime, makes herself at home, much to the Earl's chagrin. And as the artefact continues to be threatened by thieves, the two must work together to keep it safe long enough to get her brother back. And all the while trying to guard their hearts from an unexpected love.