The alarming deaths of three young men in a remote Scottish town have only one common link: all three men worked on a farm with infected sheep. The post-mortems reveal that the cause of death was acute brain disease. The government would prefer to bury this disturbing fact in statistics, but the Medical Research Council feels compelled to investigate when asked to reassure the government about the safety of British farm products. Dr. Ian Bannerman, consultant pathologist and expert on degenerative brain disease, agrees to make discreet enquiries, but he has little notion of the nightmare that lies ahead of him. As he unearths a potential national crisis, Bannerman's own safety is threatened. Human life soon becomes very cheap as the interests of sullen farmers, the nuclear industry, the mandarins of government and a force as invisible as the virus conspire to silence Bannerman rather than let him discover the truth about the crisis.