Circumstances make Helen think that Jack, the engineer and son of the road's auditor, is guilty of the theft of $50 that comes to light through a shortage in her accounts. Gypsy Joe, the real thief, gathers his followers to seek vengeance on the train crew for having thrown him off the train.
Burkett, superintendent of the Western Railway, opposes his daughter's friendship for Dick Benton, one of the company's lawyers, favoring the latter's fellow-worker, Guy Warren. Warren succeeds in putting through a scheme which results in Dick's discharge. The lovers plan to elope and enlist the aid of Helen. But Eleanor's father learns of the move and wires ahead to police officials to board her train and arrest her while he follows in his special. By a daring leap from a handcar to the train Helen succeeds in warning Eleanor of her peril, but is too late, and Helen and Dick are forced to stand idly by while Burkett starts on the return trip in his special, carefully guarding Eleanor.
Agents of a foreign power are seeking to get possession of the plans of a new aeroplane motor invented by Dick Benton. Under cover of darkness they succeed in their scheme and are escaping in their automobile when it plunges over an embankment near Lone Point.
Crossed telephone wires enable Helen to overhear a plot between Joe and Bill, escaped convicts, to join a number of Chinese who are being smuggled into the country in a freight train.
The smugglers seem in a fair way to escape on a stolen engine when Helen, unhitching a team from a nearby wagon, races down the road towards the railroad bridge from which a rope is hanging directly over the track. Standing astride the two speeding horses Helen leaps to the rope, and swaying in mid-air makes a perilous drop to the stolen engine as it dashes past.
Jud Hendricks, foreman of the construction camp, is being blackmailed by Gypsy Joe, who knows of a dark page in the Hendricks' past. Hendricks and Tom Rasom are rivals for the favor of Helen, with Tom in the lead. The latter, an engineer, is about to take his train out when he finds Gypsy Joe hiding in a boxcar.
Learning that the driver of the Comet car has been disabled on the eve of the big race, Sinton, a gambler, bets heavily on its rival. But his plans go awry when Gordon, the owner of the Comet car, meets Naroche, a celebrated French driver, and engages him to pilot the racer.
Greggs, returning from abroad with a large consignment of precious stones, thwarts the first attempt of Gentleman Joe and his accomplice to rob him at his hotel, but they follow him aboard the train the when he is alone on the observation platform they attack him, and a struggle ensues in which Greggs is finally thrown to the ground from the speeding train. Helen, riding through the hills in an auto, comes upon him before Joe and his pal can alight from the train, Greggs gives her the diamonds and tells her to speed away and rush help back to take care of his injuries.
Helen, discharged by the superintendent without justification, comes to the rescue when a flat car, loaded with dynamite, is tearing to certain destruction down the grade, bearing the mischievous son of the superintendent.
Stallings' plot to spoil the demonstration of Dick Benton's newly invented safety stop for trains seems certain of success when the locomotive is sent running wild down the tracks. Helen saves the day by climbing out on a wire stretching across the tracks and dropping to the speeding engine.
On a visit to the State Prison with Superintendent Melvin of the construction camp near Lone Point. Helen gains the friendship of Butler, a former telegrapher who had been wrongfully convicted on circumstantial evidence. Butler is soon to be released and Helen promises to aid him.