A lesser effort by Leinster but still better than most of the pulpy secret agent / evil menace stories of the period. Charlie Bell, who is of “The Trade”, is sent to South America to investigate a mysterious trouble maker called The Master who seems to be keeping hundreds of people (including high ranking members of several governments) under his control by giving them some kind of poison that can turn them into mad killers without the antidote he supplies. This is a spy adventure rather than the science fiction usually associated with Leinster even though it was originally serialized in Astounding back in 1930. The plot is pretty silly but the author includes enough local color and atmosphere to keep it reasonably interesting. ( )