In Nevada City, California during the early 1860s, stagecoach line owner Hank Liddell struggles to keep his business alive despite repeated robberies and acts of sabotage. Liddell suspects that Mark Benton, owner of the new California Central Railroad, is behind the violence, but the real ringleader is Amos Norton. Norton runs the Sacramento River Navigation Company and, desiring to squelch competition from Liddell and Benton, has ordered his henchman, poetry-writing Black Bart, to set the men against each other and destroy their companies. One afternoon, Liddell's top driver, Jeff Connor, and Jeff's pal, "Gabby" Chapman, run into Benton and learn that he is an honest man who believes that his and Liddell's companies can grow together. When Jeff tells Liddell of his encounter with Benton, Liddell refuses to listen and fires Jeff and Gabby, much to the dismay of Jo and Chick Morrison, the children of Liddell's deceased partner. Jo is in love with Jeff, but when he proves oblivious to her charms, she attempts to make him jealous by flirting with Bart, who is in Nevada City posing as Jim Trevor, a businessman ruined by Benton. Bart succeeds in entangling Liddell in a plot to ruin Benton, while Jeff and Gabby are offered a job by the railroad man when they tell him that Liddell fired them on his account. Jeff is suspicious of Bart, however, and declines Benton's offer in order to follow the mysterious newcomer. Jeff and Gabby find Bart with his gang laying in wait to rob one of Benton's trains. Bart is using Liddell's horses so that the stagecoach owner will be blamed for the robbery, and Jeff, determined to discover the extent of Liddell's involvement with Bart, foils Benton's attempt to capture Bart so that he can follow the bandit himself. Jeff and Gabby are arrested, however, and jailed for the robbery. While Jeff and Gabby engineer their escape, Chick overhears Norton and Bart discussing their plans to ruin Benton. Chick tells Jo and Liddell that Jim Trevor is really Bart, and they tell Benton what has happened. Benton and Liddell vow to work together to defeat Norton and Bart, while Jeff and Gabby race to the mountain tunnel that Bart intends to blow up to sabotage Benton's construction work. Although Gabby receives a minor injury during the fracas, Jeff succeeds in preventing the explosion and apprehending Bart and his men. Soon after, Liddell and Benton shake hands on their new friendship, while Jeff asks Jo to attend a musical show with him.