Kate Fenster, the youngest of the Fenster siblings, is surprised when The Earl of Blarney calls in her childhood promise to marry him. It had been a lighthearted bargain, she would marry him if he let her ride his prized stallion Diablo. But now both of them are of marriageable age and the careless promise tempts her more than she wishes to admit. Not quite trusting the silver-tongued Irish lord, she sets him to prove he is more interested in her heart than her dowry. Sean McCarthy, determined to join forces with Kate's brother-in-law, the powerful Duke of Kerstone, and champion reforms for Ireland in Parliament, is relieved when they finally marry on Twelfth Night. But his relief is short-lived when he gets a message that his sister back in Ireland is being accused of murder by his sworn enemy. Abandoning his new bride, Sean hurries home to rescue his sister. Unhappy to be apart from her husband, despite his letters telling her he will return to her soon, Kate travels to Ireland and finds that everything her silver-tongued husband told her was only half-true. Now it is up to her to prove to him that she is the right wife for him. The one who will stand by his side while he rebuilds his lands, regains the trust of his people, and keeps his mad, fey sister safe.