Wild Hearts by Virginia Henley

Beautiful Tabby Lamont is given in marriage to the wealthy man who takes her out of an Edinburgh orphanage. Her real identity is hidden in the past. Suddenly, her future is filled with dangerous intrigue when she is kidnapped on her wedding night by Paris Cockburn, a Scottish Border Lord called The Rogue.
Her resolve never to submit to the bold abductor melts before the sensuality of the brazen Rogue who keeps her captive at his remote castle. A dark secret sweeps them toward a blazing destiny of violence and when two wild hearts become one forever.