I Was A Communist For The FBI
I Was a Communist for the FBI, starring Dana Andrews, tells the supposedly true tale of Matt Cvetic, who infiltrated the Communist Party in the United States and reported every move back to the FBI for "nine long years". No one was allowed to know he was undercover, and both he and his family suffered because of it.
Airing from 1952 through 1954, during the height of the anti-Communist frenzy sweeping across the USA, the show was immensely popular.This is a very sober, tension-filled series, with Cvetic constantly walking a tightrope between the need to pump the "Comrades" for details of upcoming activities and the risk of getting caught if they learned his true loyalties.
You can find more episodes in the Ear Benders section.
Here is a sample of the online episodes currently available at The Old Time Radio Fan: