Setting aside the inevitable comparisons to Fritz Lang's classic M from 1931, this is an excellent noir, full of dark shadows, a creepy serial killer preying on children, and plenty of atmosphere. Nathán Pinzón, even looking a bit like Peter Lorre, is fantastic in his own right. It had me from the start in that seedy cabaret, with the montage of closeups and the sultry performance from Olga Zubarry. When she glimpses a man tossing the body of a child in the sewer through a window later, she screams, and one of the women upstairs on the dance floor says to her partner "I like it rough too, but I don't scream."
The film lost a little momentum during the police investigation which follows, though there is tension during a couple of other murders along the way (mercifully, nothing shown). The prosecutor investigating the crimes seems so upright, saying procedures must be followed and caring for his paralyzed wife - but we eventually see this unravel, as he first gets on his high horse and chastises the cabaret performer for working where she does, and then out of sexual frustration tries to force himself on her. It was a fine moment when she rebuffed him, and justified the inclusion of the wife subplot which otherwise seemed a little weak.
Along the way there is action down in the dank sewers, a shoot out in the cabaret, and carnival rides, all suitably dramatic. The whistling of Edvard Grieg's The Hall of the Mountain King by the killer added an eerie touch. Made just a couple of years before the coup that would oust Juan Perón and put Argentina under a military dictatorship for several years, the ending seems to reflect an unambiguous desire to be "tough on crime," despite the desperate speech at the end ("I don't want to but I can't help myself!"), which was cathartic. It's a film that was well done, and still has power.
