Unlikely Traitors (Ursula Marlow Mysteries)

Ursula Marlow thought she was done with death, but when her fiancé, Lord Wrotham, is arrested on charges of treason, her world is turned upside down. It is the winter of 1913, and the British Parliament, unsettled on the question of Home Rule for Ireland, is shaken over allegations of a plot to sell naval military secrets to Kaiser's Germany and liberate Ireland from English rule. For the first time, Ursula must work together with Chief Inspector Harrison to uncover the truth about Lord Wrotham's involvement, as well as his mysterious past.
 
As the investigation continues, Ursula is drawn into the shadowy world of the Irish Republican Brotherhood and a web of espionage and betrayal. She must race against time to clear Lord Wrotham's name and thwart a plot that threatens not only British national security, but also her life.