Tonton Streaming 77 Sunset Strip (1958) S1E31 - Downbeat

Stu Bailey, though acquitted of the crime of sedition for lack of evidence, has his private investigator's license revoked and goes on a drinking spree. He is then recruited by a former friend to conduct business with Communists. At the end it is revealed that Bailey had been working undercover for the U.S. government all along.