Smith is an iron-willed railroad detective. When his friend Murray is fired from the railroad and begins helping Rebstock wreck trains, Smith must go after him. He also seems to have an interest in Murray's wife (and vice versa).
Jimmy Bradley, a fireman on the old locomotive No. 99, loves Kate Murphy, daughter of the proprietress of the local lunch counter. His rival, Bat Mullins, is engineer of the new mail train scheduled to make a competition run. When Mullins overturns the new train, Bradley completes the run and earns the contract for his company by delivering the mail in record time on No. 99. A promotion to engineer helps him win Kate.
Joe Foley, charged to deliver a trainload of cattle to his employer, is forced to commandeer the engine when his engineer refuses to continue until he has observed union rest rules.
