Maryland Calvert lives in that section of Maryland divided against itself in the question of secession. Her brother, Floyd, is so strong a Northern sympathizer that he joins the Federal secret service unknown to his family and enlists in the Southern army to increase his efficiency. Her fiancé, Alan Kendrick, takes a commission in the Federal Army, although his father becomes a general in the Confederate forces. One Thorpe, a discredited Union officer, is given an opportunity to serve the Federal secret service and in that capacity, joins the Confederate army, becoming an aide to General Kendrick, whose headquarters are at the Calvert mansion. Alan Kendrick is among the Northern prisoners taken by the Confederates and when sent for exchange is recognized by Thorpe, whose bitter hatred has been aroused by the part the gallant Unionist had in his former discovery and degradation for conduct unbecoming an officer and a gentleman.