An anthropologist goes to Haiti after hearing rumors about a drug used by black magic practitioners to turn people into zombies.
Ethnobotanist/anthropologist Dennis Alan, in visiting the Amazon, receives a potion connecting him to his protective totem (a jaguar) through a series of visions, and is later guided by a jaguar from the Rainforest itself. Returned to Boston, he is sent to Haiti by a pharmaceutical corporation looking to investigate a drug used in Haitian Vodou, in the hope of using it for anesthesia.
Alan's exploration in Haiti to find the drug, assisted by the doctor Marielle, draws the attention of the authorities, so that the commander of the Tonton Macoute, Captain Dargent Peytraud, warns Alan to leave Haiti. Alan refuses to leave, and continues to investigate. Eventually, he encounters a local witch doctor, Mozart, who can produce the drug; but Mozart sells him a substitute instead.
Alan is arrested a second time by the Tonton Macoute and tortured; but again refuses to leave. Later he meets again with Mozart to obtain the true poison. A few hours before gaining this, Alan experiences a nightmare planted in his mind by Peytraud, and wakes beside a dead woman. The Tonton Macoutes then frame Alan for murder.
Alan is brought to Peytraud, who places him on an airplane at gunpoint; whereupon Mozart gives him the drug in exchange for international fame. Alan thence returns to Boston to study the components and effects of the drug.
At a celebration dinner, the wife of Alan's employer is possessed by Peytraud, who warns him of his own imminent death. Thereafter Alan returns to Haiti, where (at Peytraud's behest) he is buried alive. Having emerged he returns to the Tonton Macoute headquarters looking for Marielle. There, Alan and his jaguar spirit defeat Peytraud, prompting Marielle to say "The nightmare is over".