When Hopalong Cassidy returns to the Bar-20 ranch from a cattle sale, he discovers that his young sidekick, Johnny Nelson, has been running wild, drinking, gambling and associating with unsavory characters. One of Johnny's new friends, Shanghai Charles McHenry, finds out from him that Hoppy has brought back a lot of money, and he holds up and shoots Bar-20 foreman Buck Peters, and devises a plan to then frame Johnny for the robbery. Buck, who gave the robbers worthless money, gives Hoppy twelve hours in which to prove Johnny's innocence before he calls the sheriff, and Hoppy takes the real money to the bank, capturing a bandit along the way. Later, however, the bandits rob the bank. Johnny befriends Linda McHenry, who is the innocent daughter of Shanghai. Johnny is captured by the criminals and sentenced to a torturous death, but is saved by Hoppy. Together Johnny and Hoppy overcome all of the bandits but Sam Porter and Shanghai. Later, they meet up with both men, and Hoppy shoots it out with Porter, who shoots Shanghai before he dies. Shanghai survives his gunshot wound and promises to return the money and reform himself. Meanwhile, Johnny and Linda become better acquainted.