Pinkerton detective Red Tracy, posing as an imprisoned bank robber named Red Bannon, wins the trust of murderer Vince Ganley when they share a cell. Ganley, who is a member of a large counterfeiting ring currently under investigation, tells Red to look up his former boss, Jim Dawson, who has a ranch near the town of Sundown, when he is released. Red leaves the prison and goes to Sundown, where he runs into an old girl friend, Chicago reporter Lynn Parsons. Lynn assures Red that she will keep his identity a secret, then tells him that she is trying to get a story on Lucy Randall, a wealthy recluse. Red rides to Dawson's ranch, where his use of the gang's secret handshake secures his entry into the gang. Dawson then goes to see attorney J. Richard Spencer, who is the secret head of the counterfeiters, as well as Lucy's lawyer. Spencer and Dawson have been using their profits to buy a controlling share in a railroad company, and a large part of their ill-gotten gains has come from passing the fake money on to Lucy, who lends large sums to the local ranchers in return for exorbitant interest. That evening, Dawson takes another $10,000 in phony currency to Lucy, claiming it is the interest and the proceeds of a property sale. Meanwhile, Red accompanies the gang to a neighboring town, where they attempt to force bartender Tom Driscoll to take $3,000 in counterfeit funds in exchange for $1,000. When Driscoll protests, the gang members tear up his saloon, but Red's quick shooting prevents anyone from being injured. Soon after, Lynn tells Red that she saw Spencer with Dawson, then goes to Lucy's house, where she finally gains entry and tells the recluse that her husband Steven recently died in Chicago and left a will bequething everything to their son Wayne. Lucy explains that many years ago, Steven ran away with young Wayne, whom he left in the care of an Indian tribe while he was prospecting. The Indians moved, taking Wayne with them, and he has not been seen since. After Lynn reveals that, according to Steven, Wayne has a tattoo of the letters WR and a broken arrow on his arm, she promises to get her detective friend to help find him. When Lynn repeats the story to Red, he realizes that he is Wayne Randall, for he bears the tattoo. Red accompanies Lynn to see Lucy, and although he does not reveal his identity, he comforts her by saying that her son is alive. During the visit, he sees that the money she has been receiving from Spencer is counterfeit. When Red rides back to Dawson's ranch, he finds Ganley, who escaped from prison after learning that Red is a Pinkerton agent. Ganley is wounded during their struggle, but nonetheless manages to inform the gang about Red. Dawson tells Spencer about the new development, and they decide to steal the rest of Lucy's money and leave town. They ride out to Lucy's house, but the intrepid old woman stands up to them, along with Lynn, until Red arrives. Red bests both Dawson and Spencer, after which Lucy sees his tattoo and realizes that he is her son. Later, Spencer is convicted, and Red prepares to take Lucy and Lynn to Chicago, where he and Lynn will be wed.