Wade Davis, a Harvard scientist, investigated the claim and obtained something called 'zombie powder' from Haitian bokors. The main active ingredient was a neurotoxin found in pufferfish which could be used to
simulate death. The bokors also explained to Davis that a second poison, made from the datura plant, known as the zombie cucumber, was given to victims after they were revived from their death-like state. This kept the 'zombies' in a submissive state so that it was easy to force them to work. Davis wrote several books on the topic including the Serpent and the Rainbow. Later made into a horror film by Wes Craven.