The story begins in 1860, the eve of the American Civil War. Two young brothers - clean-cut Abraham Brown and good-for-nothing Robert Brown - work on a farm with their mother Eliza. When the Civil War starts, thrill-seeking Robert joins the Union army and leaves his brother and mother to tend the farm without him.
The Browns receive news that Robert has been killed, and the grief-stricken Eliza dies shortly afterwards. Abraham is forced to sell the farm and join the army himself; he finds a friend in kindly Sergeant Sumner, and an enemy in belligerent William Beard.
Abraham eventually learns that his brother did not die in battle with Confederates as he assumed, but was apparently killed by bandits. Abraham takes it upon himself to avenge his brother's death and abandons the army to track down the bandits.
The army sets off to catch the deserting soldier. Beard hopes to see Abraham executed; Sumner, although reluctantly joining in the persuit, hopes that he gets away.
Abraham eventually reaches the bandits, only to find that Robert, still alive, is part of the villainous gang. The bandits' leader Smith cruelly forces the two brothers to fight to the death, but this is interrupted by the arrival of the army.
During the ensuing fight Robert decides to steal a horse and escape, but his way is blocked by Beard. He draws his gun, aiming to shoot the oblivious man in the back, but is himself shot by Abraham. Meanwhile, Smith and his gang are defeated by the army.
Beard, seeing his old foe in a new light, conspires with Sumner to let Abraham go by telling their superiors that he was killed in the fight. Free, Abraham sets off on horseback for a new life.