Through the tapping of the wires a gang headed by Gentleman Joe learns of the shipment of a large amount of currency on the night express. By a daring scheme they hold up the messenger between stations and succeed in making their escape. They go into hiding near Lone Point waiting for the investigation to blow over. Through a clue furnished by Helen the railroad detective stumbles upon them but in the fight that follows he is overcome and the two crooks, boarding an engine in the yard, make their escape. Helen sets out in pursuit on her motorcycle. As she nears the speeding train a flat car looms up ahead to block her path. But a plank running from the flat car to the ground offers a solution. Without a second's hesitation Helen runs her motorcycle up the plank to the flat car, and as the machine tumbles to the ground on the far side leaps through the air to the handrail of the train. In a second she has the crooks covered with her revolver and the train is brought to a stop.
—Moving Picture World synopsis