The Heart of Maryland (1921)

When the Civil War breaks out, Alan Kendrick, an army officer born in the South, stays in the army to fight for the Union, but his sweetheart Maryland sides with the South. She soon discovers that Alan was captured by Confederates in a battle near her home and is to be executed. Although he's fighting for her enemy, she can't bring herself to let him be killed and devises a plan to help him escape.