Plantation owner Rock Dean (Bromfield) travels up the Amazon River to investigate why the workers have left in panic. Dean's guide, Tupanico (Payne) warns him of Curucu, a birdlike monster who is said to live up the river where no white man has ever been. Accompanying him is Dr. Andrea Romar ([Garland), in search of a drug which (in this story) the natives use to shrink heads. She hopes this drug will be effective in reducing cancerous tissue.