For twenty years after World War II, the United States was in the grips of its second and most oppressive red scare. The hysteria was driven by conflating American Communists with the real Soviet threat. The anticommunist movement was named after Senator Joseph R. McCarthy, but its true dominant personality was FBI director J. Edgar Hoover, who promoted and implemented its repressive policies and laws. The national fear over communism generated such anxiety that Communist Party members and many left-wing Americans lost the laws' protections. Thousands lost their jobs, careers, and reputations in the hysteria, though they had committed no crime and were not disloyal to the United States. Among those individuals who experienced more of anticommunism's varied repressive measures than anyone else was Clinton Jencks.

Jencks, a decorated war hero, adopted as his own the Mexican American fight for equal rights in New Mexico's mining industry. In 1950 he led a local of the International Union of Mine, Mill, and Smelter Workers in the famed Empire Zinc strike--memorialized in the blacklisted 1954 film Salt of the Earth--in which wives and mothers replaced strikers on the picket line after an injunction barred the miners themselves. But three years after the strike, Jencks was arrested and charged with falsely denying that he was a Communist and was sentenced to five years in prison. In Jencks v. United States (1957), the Supreme Court overturned his conviction in a landmark decision that mandated providing to an accused person previously hidden witness statements, thereby making cross-examination truly effective.

In McCarthyism vs. Clinton Jencks, Caballero reveals for the first time that the FBI and the prosecution knew all along that Clinton Jencks was innocent. Jencks's case typified the era, exposing the injustice that many suffered at the hands of McCarthyism. The tale of Jencks's quest for justice provides a fresh glimpse into the McCarthy era's oppression, which irrevocably damaged the lives, careers, and reputations of thousands of Americans.