All of England thinks Major Phillip Camden a monster—a man who deliberately caused the deaths of his squadron. But he would have preferred to die that day with his men rather than be recruited to the Admiralty's codebreaking division. The threats he receives daily are no great surprise and, in his opinion, well deserved. As nurse Arabelle Denler observes the so-dubbed "Black Heart," she sees something far different: a hurting man desperate for mercy. And when their families and paths twist together unexpectedly, she realizes she has a role to play in his healing—and some of her own to do so as well. With Camden's court-marital looming, an old acquaintance shows up, intent on using him in a plot that sends the codebreakers of Room 40 into a frenzy. With their fragile hopes for the future in the cross hairs, Arabelle and Camden must hold on to hope—and to each other—if they want to survive.