Felipe Cazals adapted the novel of Jose Revueltas that he Wrote in Lecumberri prison and displayed the corruption model of the Mexican system in jail, with his usual style of show cruelty in its greatest expression Felipe Cazals was supported this time with an extraordinary assembly of actors which intensity make convincing all he tried to show in the film, Manuel Ojeda,which head appear for the only hole in the Apando where they are prisoners,(this scene remind me Steve McQueen in Papillon) Salvador Sanchez and Jose Carlos Ruiz as the prisoners who traffic drug in the jail get in the film one of the best acting I ever seen in Mexican films until those years, Maria Rojo and Delia Casanova transmitted with naturally and freshmen the simplicity of the low-media Mexican class women, both suffer the denigrates methods of auscultation before enter at jail as visitors. Cazals didn't show in the film complicity of the policemen to introduce drugs in the jail ,that I suppose exist, just show them gave some facilities to prisoners for money…and we can hear a lawyer assure to a family that their prisoner is going to be free next week,but….. to get this they have to spread out some money for bureaucratic matters….these kind of details are some of Cazals purpose in the film, to denounce the corruption in the "legal" system in Mexico