Derived loosely from the popular-in-its-day autobiography of NY Police captain Cornelius W. "The Gang Buster" Willemse. Mary Kennedy, the daughter of police lieutenant Jim Kennedy, works for an unethical criminal attorney and is corrupted by the association. But she sees the light when she twists the law to obtain the acquittal of a client and the man later shoots her father. Mary then enlists the aid of Detective Dave Britten in hopes of bringing down the crooks for whom she works.