Broadway star Matthew Broderick knew little about his grandfather, James Joseph Broderick, and is shocked to learn about his involvement as a medic in World War I. Continuing his research, he discovers his grandmother, Mary Martindale, was a descendant from a Civil War hero, Robert Martindale, who fought at Gettysburg and joined the historic march through Georgia. While in Atlanta, Georgia, researching Robert's death, he unwittingly helps historians solve a 150 year-old mystery.