What frightening thing is happening to change the inhabitants of Balfe, an island off the west coast of Britain? Someone or something is threatening their very existence and nothing and no-one is safe. Dr. Shaw (Ian Bannen) is a leading scientist sent to the island to investigate the disturbances. Once there he tries to save the pitiable, frenzied monsters these people are becoming. Victoria Brown (Judy Geeson) the local teacher misguidedly shields these islanders from the inquisitive stranger. Someone, it seems, is tampering with nature and time is running out. What is happening to them today could happen to us tomorrow - but what is happening?