The film begins with a group of Union soldiers being captured and forced to surrender at Cold Harbor, Virginia, in June 1864. They are transported to prisoner-of-war Camp Sumter, near Andersonville, Georgia. When they enter, they discover a former comrade, named Dick Potter, who was captured at Antietam, who explains the grim realities of daily existence in the camp – primarily the lack of shelter, clean water, and regular food supplies. He also states the danger of a rogue group of Union soldiers, called the "Raiders", who hoard the camp's meager rations, and lure unsuspecting "fresh fish" – newly captured soldiers – into their area of the camp, to attack and rob them.