Twelve-year-old Caleb Johnson is left behind when his father and older brother march off to war. He wants to go with them but must stay at home and care for his mother and the farm. When his best friend, Johnny, comes home injured, he teaches Caleb to be a drummer, and before long, Caleb leaves home to take Johnny's place. He follows the army to a place called Gettysburg where he faces his greatest fears. Forced to work in the hospitals at Gettysburg, Caleb slowly comes to trust his captors only to face what he believes to be betrayal at the hands of the man he has come to trust most.