A Rake's Midnight Kiss(Sons of Sin (Campbell)‪)‬

Brilliant scholar Genevieve Barrett's secret identity as the author of her father's articles is her greatest deception-until her father's handsome new student arrives on their doorstep. Genevieve recognizes him as the masked intruder who earlier tried to steal a priceless gem from their home. Keeping the seductive stranger's identity hidden is a risk, but she's got secrets of her own to keep.
Sir Richard Harmsworth fakes a rakish facade to show society that he doesn't care about his bastard status. Yet haunted by his unknown father's identity, Richard believes the Harmsworth Jewel will prove he's the rightful heir. Intent on seducing the stone away from its owner, Richard finds himself face-to-face with a beauty more breathtaking than any jewel. But even as she steals Richard's heart, Genevieve will be in greater danger than her coveted treasure . . .