A Labor Day storm in Gettysburg, Pennsylvania, topples a rare witness tree-a 150-year-old white oak rooted near afamed Civil War battleground. Breanne Walker, a new preservationist at the National Military Park's museum, is roused from her bed to view the remarkable findings below the tree's massive roots-a diary dating back to the Battle of Gettysburg...along with a body in an unmarked grave. Breanne's boss tasks her with authenticating and connecting the two discoveries, but she is given only days, and she must work in secret so as not to alert the senior curator to whom the project rightly belongs. Succeeding in the task will validate her single-minded focus on her career. If caught with the diary, her professional life is over. But the further Breanne dives into its pages, the more the mysterious diarist seems to transform her life.