A rural town becomes prey to a strain of black slugs spawned from toxic waste dumping. It is up to the local health inspector to stop them. People are dying mysteriously and gruesomely. Only health worker Mike Brady has a possible solution, but his theory of killer slugs is laughed at by the authorities. Only when the body count begins to rise and a slug expert begins snooping around does it begin to appear as though Mike's theory might be right.