Request #69

I’m looking for a book that I checked out of the junior high school library in the mid-70’s. It looked new. I can’t remember the cover. I remember a scene where a teenage boy, who was the main character, and a teenage girl were running through a castle. The girl had a Scottish accent and she was in love with him. She died, maybe from falling off a ledge. He felt guilty because she had died trying to help him and he hadn’t returned her romantic feelings. He had just considered her to be a friend. I think that he was involved in some political intrigue. He may have come from a different time and place. Please help!