John Potter volunteers to serve the South and, disguised as a Union soldier, John starts on his mission of securing the Union forces' plans. As he steals through the Union lines he comes upon a squad of Union soldiers, and in their midst a Confederate spy. A sharp order and from the barrels of twelve guns the prisoner's punishment is meted out to him. Like a blow it dawns upon John that, if detected, that would be his fate. His courage fails him and he turns toward the Confederate lines. He runs to his home, and bursts in upon his sister, who alone is awake. A few brief words and she knows all. The boy, desperate in his shame, runs into another room; there is a muffled shot, a thin wreath of smoke tells its grim tale. She determines to accomplish her brother's mission, and flies out into the night..