In the late 12th century, two very strange children came out of an ancient earthwork at the village of Woolpit in East Anglia. They wore clothes of a colour and material never seen before, spoke a language nobody recognised, and were coloured green all over. Later, when they had learned ‘our manner of speaking’, and lost their green colour, they described a homeland which was no place on Earth. The boy died within a year, but the girl grew up and married. Is this a fairy story, or were the children runaways from some primitive tribe? In the 17th century Robert Burton included them in the astronomy section of The Anatomy of Melancholy, suggesting that they came from another world. Could it be true? Duncan Lunan has located the places in the story and traced the people, who turn out to be real, though mysterious, and very highly connected. The incident at Woolpit was one of a series at linked sites, and seems to have been anticipated by the authorities of the time. Lunan traces the green girl, traces her descendants to the present day, and investigates strange things happening in the sky and other events relating to her ‘arrival’. It suggests that in mediaeval times there might have been mass abductions from Earth, by extraterrestrials, for experimental purposes, with the knowledge if not the agreement of some of the terrestrial authorities - if so, Lunan suggests, The X-Files are set in the wrong century.