Joey and Mary Alice grow up, and then World War II comes along. Joey enlists in order to join the Army Air Corps (he still loves planes), but he has to do basic training first.
He realizes that the troop train taking him to training will pass by Grandma's town sometime in the middle of the night, so he sends her a telegram to let her know that he'll be passing through—even if he can't stop and say hi.
Joey looks out the window as the train passes by Grandma's house, and he sees her standing in the doorway waving at the train, hoping that he'll see her. He waves back.