Adolfo, a railroad engineer, is sent to a provincial station to investigate a series of thefts from trains. The investigation uncovers the existence of an unknown gang, led by a man named Ruby, who finds ways of committing their crimes in broad daylight. Director García Moreno received the full cooperation of the National Railroad in the making of the film, and it still stands today as a document of the great technological advances made in Mexico during the 1920s.