In Her Wild Highlander's Bed — Cathleen Ross

When Sir Jasper Bruce discovers a lady hiding under his bed in the castle he has just conquered, he doesn't expect to fall in love. No Scottish knight in his right mind would fall in love with a Sassenach enemy, not in 1313 when Scotland is fighting England for its independence.
Forced into a betrothal with a cruel Scot, Lady Rosamund Percy can think of nothing else except escaping to England after her betrothed leaves her stranded in a highland castle. The trouble is Sir Jasper considers her a delicious prize of war. How can she convince him to let her go when he can think of nothing else but getting her into his bed?
This is the third book in the Highlander Forbidden Fantasy Series.