Aliens are on earth, buried in the southwest of England for many hundreds of years, waiting for mankind to reach a sufficiently advanced level of technology; then when conditions suit, they will emerge. In 1991, two girls, Harriet and Emily, on a school trip to the cathedral discover the activity of the aliens. However, they are warned of the dangers by the ghost of the first bishop. The girls, using the Internet, uncover several accounts in the cathedral archives, where bones have come alive. Matters become serious when several aliens take over a policeman and army major sent to control the situation. Excavations take place as the aliens search for the craft in which they arrived to enable them to conquer the whole planet. Together with information from the diary of an eighteenth-century milliner, Mrs. Pendlebury, the two girls direct humanity's fight back.