Requiem for a Rake
Michel, Freda
"SWEAR, CHRISTABEL! SWEAR THAT YOU WILL REVILE THE NAME OF VALQUESNE TILL YOUR DYING DAY. SWEAR IT!"

And the child had sworn with all her heart and soul.

Thirteen years later, Christabel encounters her avowed enemy in the guise of Marius Gray. But by the time she discovers his true identity, it is much too late. To fulfill her oath now is to deny her heart's dearest desire. For Marius is a rake, a rogue, a cad--and the man she loves most passionately. And the man she has sworn to destroy!