Thief of Broken Hearts by Louisa Cornell

Seventeen years ago, after losing his mother and brothers in a horrific tragedy, Endymion de Waryn left his memories, his past, and the childhood friend he’d been forced to marry behind in Cornwall, vowing never to return. Now, as the Duke of Pendeen, he lives a very ordered life, just as he prefers. Having scheduled the months of August and September to conceive an heir, he summons his wife to London to do just that. When her answer is an emphatic No! he is left no choice but to break his vow and go to Cornwall to fetch her. However, a duchess who meets her husband at the door with one of Manton’s finest firearms needs more than a ducal command to be fetched.

Seventeen years ago, Rhiannon Harvey, daughter of a wealthy coal merchant, made a devil’s bargain with a ruthless duke to marry his heir the boy she loved with all her girlish heart. Wedded, bedded, and left to run the ducal Cornwall estate, she becomes the keeper of her husband’s tragic memories, owner of the family’s secrets, and a duchess not to be trifled with. Her husband’s uninvited arrival introduces her to a man haunted by the past he cannot remember and one determined, God help her, to woo her into his bed.
When Rhiannon’s life is threatened, she and Endymion must work together to discover why. His haunted memories and inept wooing may bring them together. But the secrets of the past promise to tear them apart and if they cannot overcome the lies and betrayals of their broken hearts, their newfound love may be stolen from them forever.