The great apparitions--starting with Guadeloupe in 1531--occur with a steady and increasing drumbeat across the decades and centuries. The places and the principals involved change, but the messages calling people to turn from lives of violence and sin and to seek repentance are remarkably similar. By focusing on the most widely known and documented appearances and presenting them in chronological order, the events and the messages emerge in a powerful way.
Swann shows how advances in science have placed the apparitions in a more intriguing light. One of the historic challenges concerning them was how could something which was not there be there in a way that registered on the eye mechanisms. The discovery of holography, where images that appear to be three-dimensional having bulk, shape and mass, images that can even be photographed, has provided an analogy that enlarges our perception of the physical laws and challenges the skeptics' verdict of hallucination.