Wicked Temptation by Carole Mortimer

Pru would never forgive Lord Titus Covington, Viscount Romney, for the lies and deceit which resulted in the death of the person she loved most in the world.
She might not forgive him, but she would use him, in whatever way she saw fit, in order to hunt down a murderer. Quite what she would do once she had that murderer in her clutches she had no idea, but she would find them.
Titus knew he had behaved unforgivably as far as Lady Prudence Germaine was concerned. Deceived her. Lied to her. By omission, if in no other way.
But when Pru makes it clear she intends to seek out her beloved’s murderer he has no choice but to assist her. Indeed, he finds he doesn’t want to have a choice.
Because what had started out as a deception has become a reality. As far as Titus is concerned, at least.
He is now tempted by and desires Pru with a hunger that only her complete physical and emotional surrender will satisfy.