When multi-millionaire banker John Argyle is found brutally murdered in his home, suspicions are cast upon Mary Mazuret, his adopted daughter who became the sole beneficiary of his estate under his will, Argyle having quarrelled with his son Bruce. Just as the case begins to look black for Mary, Asche Kayton, a great private detective, is called in by Bruce and takes hold of the investigation.
Basil, sent to a West Indian island to look after his brother's interests, so antagonizes the planters that they form a secret organization for the purpose of throwing off the Harcourt yoke. Irene, who has just inherited her father's plantation, refuses to join. Basil is later slain under circumstances which cause Irene to believe herself the murderess.
Lynn and Alan both love Mary. Because he deems it his duty to support his widowed mother, Lynn hides his love although he is the favored suitor. Piqued, Mary becomes Alan's wife. Both boys work in the village bank. Lynn comes upon Alan while the latter is intoxicated and helps him home. Thus Lynn meets Mary for the first time since her marriage. Alan witnesses this meeting. His jealousy aroused, the man orders Lynn from his house. Obsessed by a desire for revenge, Alan steals a sum of money from the bank and falsifies Lynn's books so as to make it appear that the latter had committed the crime.
Bob's daughter is sick, so Helen volunteers to take his place on the night run, unaware that the Blackhall gang intends to rob the train which carries a valuable gold shipment. Learning of Helen's peril, Bob and Tracy pursue the train by automobile, arriving just as the hijackers are about to explode a charge of dynamite under the rails.
Discovered by Marston in the act of robbing the safe, Mann, the crook, shoots and slays him. The murderer escapes, carrying with him a casket containing jewels. So strongly do circumstances point to Lyda, Marston's daughter, as the slayer, that she is tried for the crime. Despite the evidence of the butler and other servants, who tell of a violent quarrel between Lyda and her father just prior to the shooting, the girl is acquitted.
Mary Adams, about to visit relatives in a distant part of the country, is entrusted to the care of Manuel Bond. The girl's beauty inflames Bond, a gambler and a scoundrel. That night, when the stagecoach halts, Mary is horrified to discover that Bond has registered for both as man and wife. The gambler turns a deaf ear to the girl's frantic pleas. After locking her in the room, the scoundrel proceeds to the barroom. Mary escapes by means of the window. The girl comes upon a party of settlers. Mary joins the party. Later, the girl meets Kit, a young backwoodsman. It is a case of love at first sight and the two are married the same day.