Lieutenant Bob Warburton is wounded during an encounter with the Indians and taken to the home of Col. Annesley for medical treatment. Recovering, Bob finds that his service in the army has expired and he says he is penniless. However he is rich in romance and becomes fascinated by the Colonel's daughter, Betty. Betty, not knowing who Bob is, offers him a position as coachman, which he accepts. Many and varied are Bob's experiences as "The Man on the Box" of the Annesley coach. Becoming implicated in a plot to defraud the United States Government of important plans, he thwarts the attempts of a Russian Count and saves important plans. Betty, while visiting Bob's sister, who is a dear friend, learns from Bob's photograph who he is, but allows him to continue as coachman. Bob is entirely ignorant of Betty's knowledge of his identity. Betty's father loses his money, then Bob discloses his identity and admits he is the possessor of a large fortune in his own right. However, Betty's and Bob's romance is one of pure love and, after a series of intrigues, plots and counter-plots, all of which "The Man on the Box" foils, the couple are married and live happily ever after.—Moving Picture World synopsis