Matt Arbogast's grandfather, Paul Arbogast, died long before Matt was born. Matt never knew much about Paul, but he was always fascinated with his story. About all he knew was that Paul died as a young man after serving in World War II, and that his grandmother, Julia, never remarried.
Then Matt came into possession of letters Paul had written to Julia between 1943 and 1945. Also in the show: Growing up in the Peace Corps.