Jeffries, Sabrina. Duke dynasty #4

Sheridan Wolfe, Duke of Armitage, is determined to finally solve the mysteries behind the suspicious deaths of their mother's three husbands. Tasked with investigating a possible suspect, Sheridan finds himself in dangerous proximity to her captivating daughter, Vanessa Pryde. Vanessa thinks a little scheming may be in order--for it's Sheridan she truly has her sights, and her heart, set on. The two soon find themselves propelled into a scheme of an altogether different kind, involving a pretend engagement, a secret inquiry--and a perhaps not-so-secret leap into true love . . . - excerpted from Goodreads.com