The focus for "Brooklyn South" was the 74th Precinct in southern Brooklyn, New York City. Francis "Frank" Donovan (Jon Tenney) was the patrol sergeant who presided every day over the morning shift assignments he gave to the uniformed officers. Donovan was an informant for the hated Internal Affairs Bureau (IAB), and secretly reported to Lt. Stan Jonas (James B. Sikking), who, early in the series, transferred from being an IAB officer to the precinct captain after the officious Captain Lou Zerola (Bradford English) transferred to precinct maintenance. It was later revealed in the season that Donovan became an undercover informant 15 years earlier for IAB to protect his father, a retired cop living in Florida, from indictment for corruption.