The Key to Power (1920)

Bruce Wendell, the son of West Virginia coal mine owner James Wendell, graduates from West Point and prepares to lead a fighting unit to the front during World War I. As his father lies dying, however, he convinces Bruce to remain at home and guard the mine. Bruce's fiancée Ann Blair assumes that he is a coward and breaks off their engagement, but her brother Bobbie remains Bruce's loyal friend. Meyer, a German agent, persuades railroad president Parrish to refuse to transport Wendell's coal, but when Bruce adamantly refuses to close the mine, the spy's men decide to blow it up. While Ann is being abducted by Meyer, Bobbie is buried in an explosion at the mine. Bruce rescues Bobbie and then sends a plea to Lieutenant Parrish to rescue Ann. Meyer and his gang are captured and Ann renews her vow of love to Bruce.