A classic of the genre, almost documentary in approach - low budget, no stars, Folsom Prison locations, inmates as extras - and boiling up an explosive violence kept under perfect control. Not looking for cosy answers (in fact, final victory shades ironically into defeat), the script's prime concern is less to establish the need for reform than to demonstrate the fallibilities that militate against its accomplishment: Neville Brand's riot leader and Emile Meyer's warden are men of integrity in essential agreement as to what needs to be done, but each is attended by an evil genius - one psychopathic, the other corrupt - so that simple issues mutate into an entirely different ball game. A riveting movie.