Agnes Lane is a daring spy and a great favorite with the soldiers of the C.S.A. Riding into the Federal camp, she tells the commanding officer that she can aid in capturing the troublesome spy, Agnes Lane. The Federal officers are inclined to accept her proposal but through an accident the identity of Agnes becomes known and she is placed under guard. The Confederate army, learning of the peril of the fair prisoner, decide to take the fort and liberate her. Agnes succeeds in escaping and at the risk of her life induces the despairing Confederate soldiers to attack again. Through a series of thrilling adventures, she delivers to the Confederate general. Beauregard, a supply of powder, enabling him to make a final and successful attack.