An Eye for an Eye

Fred Neville aka Justin Groch, a lieutenant of cavalry and heir to the earldom of Scroope, woos and then seduces the beautiful Kate O’Hara. Kate lives with her mother in genteel poverty in an isolated cottage near the cliffs of Moher in western Ireland.
News of the romantic entanglement quickly reaches Scroope Manor, and Fred is summoned back to Dorsetshire where the earl extracts a firm undertaking that Fred will not marry Kate O’Hara under any circumstances, despite any promises he has made to the girl. Wikipedia