When a reporter claims that New York police are on the take letting the mob run its horse parlors at will, a shocked District Attorney Michael Norris decides to do something about it. Not knowing who can be trusted on the force, he turns to recent police academy graduates to go undercover and find the corrupt cops. Among them is Pete Harris, a 10 year Marine Corps veteran. His focus is on Lil Polumbo, recently widowed after her husband Gus' truck ran off the road. Rumor has it that Gus was heavily in debt to the mob and killed himself so his wife could collect on his insurance. When the mob learns that Harris is a cop, they try to kill him but it doesn't go as planned and kills someone close to him instead. Pete decides to get the killers at any cost.