In this Hammer horror movie, Cornish villagers become hysterical when people begin suddenly turning black and dying. When a man and his wife come to town to look into the mysterious death of his brother, they are shunned and avoided. He then discovers that his brother died of snakebite and that one woman is the incarnation of an ancient Malayan curse that turns her into a viper when she is near heat. The man is bitten by her, and to save him, his brave wife starts an enormous fire that turns the snake-woman into a complete snake that slithers off to attack her own father before allowing herself to be consumed in the flames. Fortunately, the man and his wife survive the ordeal.