Maybe the twist is that Dirtier Harry is the murderer!!!
"Genre: Detective Thriller / Dark Comedy
When headless bodies turn up all over Manhattan, a detective with the reputation of being a head case himself is called in to investigate.
A an edgy, wisecracking detective that makes Dirty Harry look meek is investigating a series of decapitations at some of Manhattan's seediest adult theaters. Along with his skittish partner, he wades into a slice of his own personal Hell as well as the Big Apple's standard core of misfits - pimps, hookers, bums and Polish metallurgists - to find the man behind one very sharp blade. Brutal murder is not without a sense of humor."