After binding Helen to prevent her from stopping the express train to have it await an armed guard, crooks board the train, disable the messenger and dynamite the safe. Helen later takes a short cut in an auto and overtakes the train, but the crooks leap from the speeding train into her car before she can warn the engineer and train crew.

Jim Owens, a sergeant in the Union army, finds the body of a dead Confederate, whose resemblance to himself is so great that he is startled. He makes an examination of the man's clothes and finds a letter addressed to John Calhoun, 7th Regiment, Virginia Volunteers. The letter is from the man's mother, telling him that her world is very narrow now that she has lost her eyesight. Never having known a mother's love, Owens decides to impersonate Calhoun, feeling that the mother will not recognize that he is not her son, now that she is blind.

Disguised as car repairmen, Mealius and Denney get aboard the express car, overpower the express messenger and steal a valuable package being forwarded to Arlington. Helen sees the crooks jumping from the car when it stops for water at Lone Point and gives the alarm.

Clifton Boyle, a lead actor in a disbanded theater troupe. Boyle returns home to find his sister dying; she reveals she married Harold Welles, another actor, who abandoned her and their deceased baby. Boyle swears vengeance on Welles. Boyle tracks Welles down and uses the theatrical world to enact his revenge, making a real-life drama out of his sister's tragedy.

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.

Fearing lest Cameron's horse beat the pony he has plunged on, Tony Dorgan orders one of his men to bribe the stableman to drug the animal. Saratoga Johnny tries to carry out Tony's order, but receives a beating at the hands of the irate Cameron employee.

Hume and Frintz, while riding in a boxcar, see a trunk in the unguarded baggage car of a passenger train. By a daring leap from the freight to the passenger, Hume steals the trunk, throws it into one of the boxcars, and then leaps back. The trunk is missed and the loss reported from Helen's station.

A college boy's prank imperils the life of the railroad president's son who has worked his way up to engineer in his course that starts "from the bottom." Tied to the engine, the son is speeding on a runaway engine toward the Flicker Creek bridge which has been swept away by the floods.

Half-breed Nor is loved by French Canadian Jacques but when they quarrel, she meets Englishman Cedric Ralston who has been jilted by his fiancée Margaret for his elder brother, Lord Ralston. Later, Nor and Cedric are married, but on the day of their wedding, Cedric hears of his brother's death, and he goes to England, taking Nor. Unhappy she realizes Cedric’s heart belongs to Margaret and Nor returns to her mountains and to Jacques.

Bull, Reno and Red make a getaway after holding up the Limited. Helen later sees the men and summons the detectives. The convicts escape from the trap and board a passing freight. Helen also succeeds in getting aboard. The train crew discovers the fugitives. Reno, in charge of the valise containing the loot, throws it into the boxcar ahead.

Confronting Helen at the Lone Point Switch Tower, Denning and his pal imprison the girl in a clothes closet and then steal everything of value. In making their getaway, the crooks accidentally upset a lantern and set the tower afire. Helen, by picking the lock in the door with a hairpin, barely escapes death in the flames.

Dawson, a newcomer to the division, meets Helen while the girl is riding in the freight engine with Star, his engineer. Helen ignores the fireman's offensive stares, knowing that trouble would instantly result, if she reported the matter to Star. The following day, Dawson approaches the girl telegrapher and, seizing her in his arms, kisses her.

Borden, who nurses a secret grievance against Helen, awaits an opportunity for revenge. The girl telegrapher receives a message which informs her that the freight of which Easton is conductor, is to wait at Workman until the Fast Mail passes.

#61 in the Hazards of Helen series

Detective Strong is warned that an attempt will be made to free the crooks he is taking to the penitentiary. In spite of his vigilance, the prisoners escape when confederates start a gunfight on the train. Strong and his men scour the countryside for the fugitives.

Spang, a tramp telegrapher, is knocked down by a freight car while walking up the siding near Lone Point. Helen witnesses the accident and by quick work saves him from being run over. The girl is later transferred to the shop's office and, due to her influence.

After robbing the bank at Orlock, Cherry and Newton make their getaway. When on the outskirts of Lone Point, the men cut the telephone wires. Helen, however, learns of the robbery. Never suspecting that the crooks are headed for the station, the girl is taken by surprise when Newton and his pal hold her up.

Abigail, the pretty daughter of a village school teacher, and Jared Guild are lovers. Bertha comes from the city to visit in the little town. Her charms prove too strong for Jared, who neglects Abigail to dance attendance upon the new belle. The country girl is broken-hearted, though she hides her sorrow from her erstwhile sweetheart. A wealthy young planter, however, soon cuts out Jared with Bertha.

Tony, a half-breed Mexican is kicked from pillar to post, but he grasps a chance for revenge on society when he peers through the station window and sees Helen, the operator at Lone Point, opening the express company bag containing a valuable shipment to a local rancher.

The Girl Who Doesn't Know is a 1916 American silent film directed by Charles Bartlett.