New ranger Cotton Buckmeister is assigned by Judge Larkin to return a strongbox of official documents to Uvalde. Chad and Joe are to accompany him. Judge Ike Macallum ruthlessly rules Uvalde and has illegally brought charges against many people in order to blackmail them. So both Macallum victims and his henchmen are after the strongbox. During the journey Chad and Joe discover that Cotton also has an interest in the strongbox as he is ""wanted"" for breech of promise when he refused to marry Judge Macallum's sister Ada. A shootout occurs before Parmalee can arrive with Judge Larkin. Joe ends the gunfight by blowing the strongbox up with dynamite. All of the documents are destroyed except one - Cotton's. Court is held and Cotton is found guilty and Chad and Joe are appointed as supervisors.

Reese and Cotton run off two outlaws intent on forcing the inhabitants of San Diablo to divulge where the fabled treasure is hidden. Dandy Davis is wanted and Cotton heads back to Laredo with him but Dandy fills Cotton's head with stories of the treasure and how Reese will beat him to it. Reese has stayed behind as he knows the other outlaw Ben Slick will be back to raid the town and the San Diablo citizenry has asked him to teach them to defend themselves. Reese becomes general of their ""army"" and is even given a uniform. When the outlaws return Reese and the citizens defeat them and Reese and Cotton are able to return to Laredo.

Joe, Erik and Cotton Buckmeister meet printer Lemuel Beamish, who asks to travel with them the next day. Unknown to the rangers Beamish has three men following him. Beamish's cinch breaks and Cotton stays behind with him, spending the night at an abandoned fort. They are attacked and Beamish is killed. Before he dies he recites a nursery rhyme Cotton is to repeat to Beamish's niece when he delivers his belongings to her, which include a satchel of money. The money turns out to be counterfeit and the rangers suspect that the three men and possibly the niece are after something else, such as engraving plates. The nursery rhyme may be a clue to where they are hidden but Cotton can't remember how it goes!

Joe's old friend John Bright Star is accused of killing Clara McDermott, a woman who had befriended him. Joe and Cotton are picked for jury duty and Judge Lamprey is presiding, his family was killed by Apaches. After a quick trial Joe is the lone not guilty vote but is soon joined by Cotton and muleskinner Abbie Heffernan who has ideas about marrying Cotton. While the jury deliberates Parmalee sends Chad to look for evidence that will corroborate Bright Star's alibi. Parmalee, Eric and the Judge fend off a lynch mob and Parmalee concocts a re-enactment of the crime he hopes will catch the real killer.

Chad, Joe and Cotton Buckmeister are offered a $50 bonus to transport a bottle of Nitro Glycerin and the Professor who invented it to an army fort. A quick-change artist keeps trying to steal the Nitro and eventually succeeds. The Rangers manage to capture him and get the Nitro back.