Black Mystery

Written by Terence Roberts

Copyright 1961

First published in The Saint Mystery Magazine (UK), November 1961 and then in The Saint Mystery Magazine (US), April 1962. 
What were the natives of the region smuggling in those small vials to the German submarines in the Caribbean that were so heavy and yet so small? That is what Tar and his new acquaintance, Raies, must figure out. That, and how to stop them.