Hoping to increase its box-office allure by adopting the title of a popular song, Deep in the Heart of Texas (clap!clap!clap!clap!) was the first Johnny Mack Brown western of the 1942-43 season. The plot concerns a group of insurrectionists who intend to keep Texas separate from the rest of the USA. Brown is cast as Jim Mallory, son of insurrectionist leader Colonel Mallory (played by William Farnum, who was often called upon to play Brown's dad). At first sympathetic to the separatists out of loyalty to his father, Johnny ultimately realizes that the movement has been corrupted by a criminal element. With the help of governor's emissary Brent Gordon (Tex Ritter), Johnny is instrumental in restoring the Lone Star state to the Union. The title tune is sung con brio by the Jimmy Wakely trio.