Peregrine Cavendish, 12th Earl of Enzie, has made a devil's bargain: he's going to sell Rowena, Isla's beautiful and innocent younger sister, to a known murderer in exchange for forgiveness of his debts. Tristan Mountbatten, the infamous Duke of Darkling Reach, has a habit of marrying such women and then disposing of them...horribly. For this and other reasons, there are rumors. That he practices the dark arts; that he's a necromancer; that he is, in fact a demon. And studying him, this notorious politician and realm builder across the table, Isla can believe it. Believe it all. Because she knows, even from that first introduction, that Tristan Mountbatten isn't human. No one else seems to have noticed the obvious, but Isla has...and is terrified. For herself, but more so for the sister she loves. The sister who's been more of a daughter, the sister for whom she'd sacrifice anything. So Isla makes a devil's bargain of her own.