Wicked Surrender by Carole Mortimer

Eight gentlemen known far and wide as The Sinners. Also agents for the Crown, they are each tasked with discovering which of eight ladies in Society has been acting as a spy for Napoleon. By fair means or foul.

Dante St Just, the Duke of Huntley, is less than pleased when he is asked to investigate the beautiful widow, Lady Isabella Aston. The two knew each other seven years ago, and parted badly. But neither can Dante bear the thought of passing Bella’s name on to one of his friends. If anyone is to seduce Bella into revealing whether or not she is a spy, then it will be him or no one.

Bella is surprised, and then suspicious, when Dante St Just calls unexpectedly at her home. She becomes alarmed when, that very evening, he carries her off in his carriage.

Alone with Dante, with not even a servant to act as chaperone, how is Bella to resist the helpless attraction she has always felt toward him?