I agree with the only other individual who has commented on this movie, it's a real 'mafia-action' classic from the early seventies and is gritty, well plotted and acted and has a very high body-count !
Our hero (or rather anti-hero), is a hit-man for the mafia, who proves his worth by rubbing-out half of a rival gang, whilst they were enjoying a private screening of some Scandinavian porn, launching grenades from the projection room- into the auditorium.......
I don't want to give away too-much but this film has enough twists and turns -double and treble crosses to keep any fan of the genre glued to the screen.
Also has a great score by Luis E. Bacalov - the main theme comes in times of action and thunders by like an express train carrying an angry Keith Moon, backed with fuzz-guitar, then flips into frantic jazz piano (has to be heard to be appreciated).
Has to be seen too !