Police Squad! S01 E06 Testimony of Evil (Dead Men Don't Laugh)

"There are 8 million stories in the Naked City. Here are six."

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.