An obsessive, insubordinate homicide cop is convinced a serial killer is loose in the Hollywood area and disobeys orders in order to catch him.
 
Picture another Dirty Harry sequel, but without Clint Eastwood starring in it.
 
FUN FACT:  Originally filmed under the book's title 'Blood on the Moon', Atlantic, the studio behind the picture, decided to re-title the film "Cop" because they were concerned that people would think it was a slasher movie.