In the face of seriously declining railroad passenger travel, engineer Tom Caldwell presents to the president of the CB&D Railroad, B.J. Dexter, a design for a revolutionary diesel-electric train that will increase efficiency and lower costs. Dexter opposes change, however, and the railroad's conservative board of directors agrees with him, rejecting Tom's design. Tom quits in frustration. Sure that Tom's theory is sound, Dexter's daughter Ruth convinces Ed Tyler, a locomotive manufacturer, to look into Tom's design. Tyler is impressed with the concept and initiates immediate construction of a prototype. Soon Tom and his team prepare the Silver Streak for a well-publicized trial run with Dexter and Ruth aboard as passengers.