The Mysterious Marquess by Grace Burrowes

The Prodigal Peer…
Lucien, Marquess of Lynnfield, disappeared from the family seat nearly a decade ago, and now he’s back, ready to take his inheritance in hand. Questions swirl–Where was he? Why return now? What sort of man has he become?–and Lucien can’t offer much in the way of explanations. All he knows is, the dearest companion of his youth, Lady Penelope Richard, is being courted by a handsome cad, and Lucien cannot allow her ladyship to waste her future on a scoundrel.

Or the Return of the Rogue?
Penelope hasn’t seen Lucien for years, but she’s been too angry with him for abandoning her to forget him. He broke her heart when he left the first time, and she is quite, entirely, completely over him–almost–until old passion stir backs to life, hotter and more dangerous than ever. If Lucien and Penelope are to share their hearts as well as searing kisses, they will have to fight their own worst fears and outwit an enemy who will do anything to keep them apart.