The Viscount and the Thief by Emma Orchard

Sophie Delavallois is the new companion to the ageing Dowager Marchioness, but she also has another reason for coming to the infamous Wyverne mansion, one that will shake the family to their core.
Lord Drake left his childhood home many years ago, and only returns now to see his beloved grandmother. He takes little interest in the goings on of the house, until the arrival of Mademoiselle Delavallois. There’s something about her that he can’t put his finger on; it’s as if he’s seen her before, but surely, that is not possible…

Sophie is also drawn to Drake, but he is a Wyverne, and she cannot allow herself to fall for him, because her intentions towards the family are resolute – revenge. But inside the walls of Wyverne Hall, she discovers the rumours about the family barely scratch the surface, and she can’t escape the dangerous allure of the Viscount.