Nancy finds mystery in everything she does. In the novel Nancy and her friends along with her father head to Scotland on family business and to solve the mystery of the missing heirloom. Nancy is warned not to go to Scotland, but she ignores the warning. Nancy finds strange things in Scotland like the people. She and her friends, Bess and George, visit Nancy's great-grandmother from her mother's side (who Nancy's never met) at an estate in the Scottish Highlands. While there, Nancy becomes involved in the mystery of missing flocks of sheep and a mysterious bagpiper has been spotted. Clues leading to a discovery in an old castle and a prehistoric fortress lead to the mystery's solution.