Sally McQuire worked for an unusual organisation. She was an undercover agent for the I.P.F., but her friends knew her only as a scatter-brained night club dancer. Then came the Thing. At first there were just off paragraphs in provincial papers. A cow disappeared. Fish stopped biting. Finally Jon Vardo, a shepherd, vanished without a trace. The I.P.F. put Sally on the track. She discovered a strange common denominator linking the events. There was a mathematical and geographical sequence. Sally arranged to be at the next danger zone, and then she too vanished. This is a story of humanity at its best, locked in a life and death struggle with a cruel, cold culture of Beings from the Beyond. This is a story of humanity fighting against incredible odds and fantastic weapons. Can the mind of man hold its own against deadly, sinister Intelligence from beyond the stars?