The Legend of Robin Brodie (The Highlanders #2) by Lisa Samson

Introverted and shy, Robin Brodie carved out a solitary existence in the woods near Castle Lachlan. He avoids all contact with others but for the friendship of one woman, Alix. When Alix becomes engaged to Duncan Campbell, she has little time for Robin--but he never forgets her. When Duncan faces mortal danger, will Robin make the ultimate sacrifice for the woman he loves?