High School History - The Treasure (fifth in the high school series)

An ordinary history assignment leads Arianna to an old country school building on a Civil War skirmish site, and her younger sister alerts her to a missing girl. Gradually she realizes that the building houses a mystery, and the surrounding grounds must give up their Civil War secrets so that she can complete her essay. But a farmer, two reluctant librarians, and a hair barrette stand in her way.