I Spy a Duke

In the first in an adventurous new series, USA Today Bestselling Author Erica Monroe introduces the Covert Heiresses: women who by day are the talk of the ton, and by night England's top spies.
SHE WANTS REVENGEWhen bluestocking Vivian Loren becomes the governess for the wealthy Spencer family, she's hunting for clues about the murder of her brother, not romance. But Vivian didn't count on one thing: James Spencer, the intrepid Duke of Abermont, who has a tortured past of his own.

HE NEEDS A WIFE
As head of Britain's elite intelligence agency, James can't afford the scrutiny the Marriage Mart would bring to his family once the Season starts.  After discovering Vivian's quest for vengeance has made her a pawn in a treacherous plot of one of Napoleon's most deadly spies, James realizes they can help each other. She'll become his duchess, and he'll keep her safe. 
What begins as a marriage of convenience quickly becomes anything but as the enemy spy closes in on them. When both husband and wife have dark secrets, love may be the most dangerous mission of all.------I Spy a Duke is a dark, sexy Regency romance with suspense elements. While it is book one of the Covert Heiresses series, it can be read as a standalone full-length historical romance.