The pace is quick, the violence is rough, and the visual style is documentary as Padilha hammers home his point: Someone is forever in the pocket of someone else as The System constantly adapts to protect itself.

When this Enemy Within settles into key action sequences, such as a stunning nighttime ambush or a daytime battle against Fabio, it becomes wildly entertaining.

Padilha's film offers no easy answers, but the title is a tip off as to where at least his sympathies lie.

Moura returns as senior security officer Nascimento in this chaotic, knotty sequel, which was a critical and commercial smash in its native Brazil.