The FBI infiltrates one of their agents, Matt Cvetic, into the US Communist Party. This causes big problems in the normal life of the agent. Nobody knows, including his family, that he is in fact working to expose a large-scale plan to have Communists in key positions in industry and unions.
I Was a Communist for the F.B.I.
In Pittsburgh, PA, an F.B.I. agent works to undermine the Communist party, but his brothers and his teenage son think he's a real Red.