The real Matt Cvetic was a borderline alcoholic with a nasty disposition (he once allegedly beat his sister-in-law so badly she required hospitalization). But Cvetic was also a fervent anti-communist, and so, for a brief period in the early 1950s, he was a folk hero. I Was a Communist for the F.B.I. is the semi-true story of how Cvetic (played by Frank Lovejoy) renounced his friends and family and embraced the Red cause--on behalf of the F.B.I., for whom he was a volunteer undercover agent. The film recounts how Cvetic used his job as a Pittsburgh steelworker to contact various American Communist cell leaders, and how he exposed their insidious plans to overthrow the American government. Since the script infers that among the Reds' "subversive" plans was the Civil Rights Movement, I Was a Communist for the FBI is an embarrassing experience when seen today. Cvetic's memoirs were better dramatized by a 1951 radio series of the same title, starring Dana Andrews.
by Hal Erickson synopsis