The daughter of an Irish marquess, Lady Jill Lynch prefers to leave the royal duties to her older brother, Robert, instead, focusing on her career as an accomplished book editor.

That is when she's not called upon for her other skills as a professional assassin.

Unaware of her carefully guarded secret, a dangerous man, bent on revenge against the marquess, targets Lady Jill, knowing her death would cripple her father.

After narrowly escaping an attempt on her life, Lady Jill enlists help from her American counterpart, a mysterious man known only as Jones. Together with his own unique team, Lady Jill and her own counterpart, a man known for his penchant for secret passageways as much as for his love for Jill, form a plan to eliminate the ensuing threat. All while dodging the prying eyes of Lady Jill's parents, as well as those of an exceptionally curious butler.

Time is of the essence; lives are at stake. Not only must Lady Jill protect her family, but she must also protect the man she loves from dying one more time.