Anthropologist Hess Green (Duane Jones, NIGHT OF THE LIVIG DEAD) is conducting research about the Myrthians, a fictitious ancient African nation of blood drinkers. One day, his psychologically unstable assistant (played by the director Bill Gunn himself) stabs him with a dagger that the Myrthians used for their ceremonies before killing himself. The next day, Green’s wound is healed but he himself becomes possessed with the need to drink blood. When the assistant's wife comes looking for her husband, she and Hess explore the possibilities of his new state of being.