A series of frightening images demonstrates how the fly manages to transmit all kinds of diseases. At first, it looks like a conventional documentary, where a doctor and his assistant perform different manoeuvres to demonstrate with practical examples the risks carried by the insect. But rapidly, the film starts employing microphotography to show the monster in action, contaminating everything and reproducing in an abject and irrepressible way.

According to information of the time, the film was part of a series of prophylactic documentaries about different illnesses and was exhibited for years in morning screenings for schoolchildren (who most likely never forgot it). The scientific advisor of the series was a so-called Dr. Barbara.

A 35 mm. print in very good shape was conserved at the Museum of Film Pablo Ducrós Hicken and preserved in 2009 thanks to a contribution by Filmoteca Buenos Aires. (Fernando Martín Peña)