A Gentleman in Challenging Circumstances by Grace Burrowes

A legacy of lies…
Lord Julian Caldicott, still recovering from his years at war, is tasked with investigating the circumstances of a small boy who could be either the salvation of the Waltham dukedom or a pawn in a scheme to sink the Caldicott family in endless scandal. The boy is alone in the world, though any one of several women might be his mother, and they all claim that Julian’s brother, the late Lord Harry Caldicott, was the child’s father.

Or a heritage of honor…
To uncover the boy’s parentage, Julian must face demons from his own past, solve puzzles left behind by Lord Harry, and thwart enemies who wish the lad harm for reasons of their own. His investigation takes him from barracks, to brothels, and to Hyde Park by dark of night. The longer he searches, the more tangled—and dangerous—the mystery becomes, for Julian and for the innocent child who deserves to know the truth of his own birthright.