Police Squad!

Testimony of Evil (Dead Men Don't Laugh) 1 Season 6 Episode

A struggling comedian owes money to the owner of a nightclub. When his body is discovered at the bottom of a cliff in a car crash, all the clues point to suicide. It is later discovered that the comedian was also a police informant on a drug ring he infiltrated at his nightclub. Frank steps in and takes the place of the deceased at the nightclub in order to gather more clues.