A Thin Line (The Reluctant Lords #2)
Tammy Jo Burns

Now time and circumstances have changed them both. By a series of unfortunate events, Gabriel has become the Duke of Hawkescliffe and sees himself resigned to a loveless marriage. Until that time arrives, he will continue to serve in the fight against Napoleon as an Agent for the Crown.
When Mikala Simmons overhears a conversation that sounds as if Gabriel is trading secrets with a foreign agent, she is torn. Should she tell someone or confront the man himself? Only as she becomes further embroiled in the subterfuge and her life hangs in the balance will Gabriel have to decide what is truly important. Society, the Crown, or the woman of his dreams?