A gangster has an organization man become a cop, with being an inside Cop as the motive, and rising in the ranks for GOOD info.
While the Cops have a cop become an organization man. Rising to be the gangsters right hand man...
The cops want to clean house as they get a tip there is a gangster being a high ranking Cop.
The gangster wants to clean house too, getting a tip a cop is high in his organtization.
Ironically each insider, becomes the cleaner for each opposing organization.