Chuck Norris stars in his first suspense film as the tough, street-fighting sheriff of a small Texas town terrorized by a psychotic killer. Sheriff Stevens (Norris) is faced with the dilemma of stopping the invincible murderer, made virtually indestructible through genetic engineering. A young group of researchers is responsible for developing the genetically altering serum, and the head of the research institute is determined to continue the experiments, regardless of the consequences.