Mexico's hidden class codes and conflicts are ruthlessly exposed in this clever murder mystery, winner of the Best Director award for Jorge Fons at the 1976 Berlin Film Festival. A night watchman at a construction site is brutally murdered; when the police investigate they find that the murder is only the beginning. A web of corruption spreads from bottom to top, from a thieving foreman to an inept engineer, all the way to the company owner, if only the police can be bothered to look. Veteran actor Ignacio López Tarso (also seen in Macario) lends his grizzled presence to this tale of labor unrest and worker oppression, anchoring Fons's constantly shifting parallel narratives with a toughness as considerable as the setting itself.