Police Squad!

Rendezvous at Big Gulch (Terror in the Neighborhood) 1 Season 5 Episode

The mob sets up an "insurance" scam that threatens several businesses and residents. Frank and Nordberg go to investigate. After a dance instructor is beaten up, they set up their own shop - a key-making and locksmith store - and go undercover. When the mob stops by to offer them "insurance", Frank dismisses their threats and the mob strikes their store. Frank ends up having the key to stopping the crime wave, largely because of the key-making and locksmith shop he and Nordberg set up.