Someone who only knows of Esper, coming to this film with n open mind will I think be rather surprised at how good it is. Far from being a mindless hack who churned out any oddly rubbish for the so-called "exploitation" market, Esper very clearly had aspirations of an artistic kind and experiments with European-style montage (not simply "irrelevant footage" as one reviewer seems to think), very rare in US film, and with some interesting chiaroscuro effects. This sometimes makes the continuity a little dodgy but gives the film a certain quality much superior to the general run of "Poverty Row" films.
By contrast, his follow-up, Maniac, which dabbles in horror/melodrama somewhat in the line of the contemporary British star Tod Slaughter, is not nearly so good a film and gives a yardstick by which to appreciate the real qualities of Narcotic.
What one also sees most clearly with Esper at his best is the way in which the "exploitation" film is really a sort of alter ego, a shameful double of the US industry as a whole. Consider for instance how a typical police-operation gangster film uses essentially the same tropes - one part of the film follows the police or the FBI (emphasising the evil of the gangsterism in narrations that are not unlike Esper's supposedly didactic intertitles, while the other part of the film allows the viewer to enjoy the antics of the gangster.
Genre after genre in US cinema in fact exhibit the same essential traits as the "exploitation" film because it is what, between censorship rules and greed for high profits, the US film industry had essentially learned to be and Esper's films are simply a microcosm, Hollywood denuded of its glamour.
Note two how this film is interestingly rooted in the memory of Hollywood with silent stars Paul Panzer and Josef Swickard and even the son of film pioneer Stuart Blackton amongst the cast.