coinciding with the emerging popularity of movies that deal with anything related to serial killers , relentless , 1989 low budget thriller about lapd detective sam dietz , played by character actor leo rossi , spawned three more sequels . 
relentless 3 , third in the row , features sam dietz again , but this time detective , who had to catch vicious serial killer in his very first case , doesn't want to deal with similar line of work . 
divorced , demoralised and transferred , he reluctantly returns to his old post when los angeles becomes a hunting ground for another serial killer , and evidence indicate connection with one of dietz's old cases . 
to make things even more interesting , it seems that the killer deliberately stages murders in order to bring dietz to the investigation . 
fans of the british tv films and mini-series like prime suspect or cracker would probably see a lot of similarities relentless series of movies . 
they both feature vicious psychopathic killers , yet also give a lot of , usually depressive , details about chief investigator's private lives . 
this one isn't an exception , but similarities with british television are only in content . 
the execution and style is different , which makes this film mediocre piece of entertainment at best . 
useless , gratuitous erotica also doesn't help either , obviously making this film longer than it should be . 
the actors are good , though - leo rossi is fine as usual , and william forsythe plays one of more compelling villains in his career . 
signy coleman as dietz's love interest , is , on the other hand , quite miscast . 
but she won't have to worry about it in the future career , since relentless 3 wasn't supposed to be anybody's finest moment anyway .