If Not for the Duke by Lana Williams

Can she keep her secret from the suspicious duke?

While thrilled her older sisters are happily married, Lena Wright doesn’t expect that future for herself. Not when her ability to foresee events causes her such distress. How unfortunate that her intuition places her directly in the path of the grumpiest man in all of London–the Duke of Renwick.
Sterling Dunworth, the Duke of Renwick, learned not to trust others from his father. Lena Wright is intriguing, and he’s grateful to her for befriending his shy sister, but a secret lurks in her beautiful eyes. If only he could remember that after their first kiss.
Lena is dismayed to learn His Grumpiness has launched a search for treasure on Oak Island. But when the famous treasure hunter the duke employs to lead the dig claims instant success, Lena refuses to remain silent.
All Lena wants is to unveil the treasure hunt as a fraud and protect her father’s legacy. She has no desire to hurt Sterling or his sister. Yet with each day that passes, it becomes clear she can’t manage both.