Catching up on some recently read books - this is historical romance / crime fiction from New Zealander Author, Jude Knight.
From the Blurb:
Prue's job is to uncover secrets, but she hides a few of her own. When she is framed for murder and cast into Newgate, her one-time lover comes to her rescue. Will revealing what she knows help in their hunt for blackmailers, traitors, and murderers? Or threaten all she holds dear?
Enquiry agent David solves problems for the ton, but will never be one of them. When his latest case includes his legitimate half-brothers as well as the woman who left him months ago, he finds the past and the circumstances of his birth difficult to ignore. Danger to Prue makes it impossible.