 Fade into the office of the President of the Lamy & Yuma Railroad where the prexy Thompson (Jack Cowell) and a group of stockholders, including cattle ranchers Senator Rogge (Vincent Dennis), "Dynamite" Murray (Lloyd Ingraham) and Tracy Paine (George Ball), are discussing the location of a new right-of-way for the line. It quickly develops that the L&YRR will save a lot of money running through the Wagon Wheel Ranch, but owner "Rocky" Brown (Forrest Taylor) refuses to sell. Rogge and Paine promise to return within thirty days with the secured right-of-way,a promise that right away tells anybody that s paying attention who the bad guys are or will be. Fade next to Brown counting his herd and surprised to find he has a lot more than he can account for. After consulting his sister Ruth (Connie Bergen) and his sweetheart Sheila Murray (played by and credited to silent actress Peggy O Connell, billed as O Connel, and not by 1950 s actress Peggy O Connor as the source that changed this credit seems to think), Brown decides to notify the Cattleman s Association that someone is using his brand and adding cattle to his herd sans his knowledge or consent. The Association Chief (John Elliott) sends Johnny Argyle (Rex Bell) to investigate, using the assumed name of Tucson Smith. (Oh great, another title to add to the Three Mesquiteers series!) Tucson/Johnny learns that Brown, before coming to the area, had been framed and convicted on a rustling charge;has a fight with Paine;stumbles across a hidden rifle, a box of cartridges and several steel heel plates;intervenes in a fight between honest rancher Murray and Brown;finds some brand-altered hides; wounds an ambusher but can t find him; threatens the RR President with blackmail;has an in-depth discussion about a 38-55 rifle with the Sheriff (Horace Murphy) and Brown; is ambushed again but this time takes two prisoners; makes a turncoat witness out of Rogge s co-conspirator Paine, and saves Brown from being hanged for the murder of Murray. All in a days work for a Cattle Association detective.