Book three, The Promise, begins when Gracie and David take off for their honeymoon in her Uncle Rich’s RV. As they get to their first stop near St. Louis, Gracie gets a phone call from her cousin Angela. She says she has something for them—Great-great-grandma Mary's Wedding Ring quilt, made during WW1, as well as a Hope Chest with a false bottom, and some great BBQ. Gracie and David investigate what happened during the first World War to a group of soldiers from Jubilee Junction and how the war affected those back home, including Grace’s great-great-grandmother Mary, the other narrator.

It's 1917. Mary Carlson is a senior in high school. She has her first romance with Charlie O'Connor who wants to marry her. However, with WWI raging in France, her whole town is concerned that many of the young men are about to be sent overseas.