Jacques Vallee, scientist and astronomer, argues that the appearance of UFOs, their landings and the many first hand accounts of the characteristics and behaviour of their occupants can be likened to the myths and legends from all ages and from all over the world that feature supernatural beings: angels, devils, elves or giants according to local folklore or belief. He sets out to build a bridge between two clusters of rumours, observations and reports: on one hand, the claims of men and women who state they have observed such beings and on the other, the large amount of similar data that has come to us through tradition.