Holy Island - Facts

 The events of the novel take place on Holy Island or Lindisfarne in Northumberland.  The island is an Area of Outstanding Natural Beauty and a hotspot for historical tourism and bird watching. The island is accessible from the mainland at low tide by means of a causeway.

The castle is where Anna is taken at the end of the book. Lindisfarne Castle is a 16th-century castle located on Holy Island, near Berwick-upon-Tweed, Northumberland, much altered by Sir Edwin Lutyens in 1901. 

Lucy's body is found in the priory. The Lindisfarne Abbey was first established in 634 AD. The island served as the site of a monastery for roughly 900 years. The site, most of which has fallen into a state of ruin, has since become a popular tourist destination and focus of pilgrimage journeys.  Remains from the pre-Norman/Anglo-Saxon era can be found in the chancel wall of this church. 

In the town there is a statue of St Cuthbert. Cuthbert of Lindisfarne (c. 634 – 20 March 687) was a saint of the early Northumbrian church in the Celtic tradition. He was a monk, bishop and hermit. 

The characterms mention that St Cuthbert was exhumed and found in the same state ten years later. He was buried beside the altar at Lindisfarne and when the monks dug him up some years later, according to the Venerable Bede, instead of the skeleton they expected to discover, they ‘found his body entire, as if he were still alive, and his joints were still flexible, as if he were not dead but sleeping.’

Anna is a professor of history in Durham University. Durham is a city in northeast England, south of Newcastle upon Tyne.

The police find traces of a drug, obtained from the seeds of the plant called morning glory. The seeds of many species of morning glory  are used as psychedelics. The seeds of morning glory can produce a similar effect to LSD when taken in large doses.

 After Rob's death, Anna talks about some pagan rites. For example, the Celtic druids used a wicker figure which filled with people and burnt them alive. A wicker man was purportedly a large wicker statue in which the druids  sacrificed humans and animals by burning. The main evidence for this practice is a sentence by Roman general Julius Caesar in his Commentary on the Gallic War (1st century BC)

Also Carthaginians sacrificed children at Tophet. In the Hebrew Bible, Tophet o is a location in Jerusalem in the Valley of Hinnom, where worshipers engaged in a ritual involving "passing a child through the fire", most likely child sacrifice. Most scholars agree that the ritual performed at the tophet was child sacrifice, and they connect it to similar episodes throughout the Bible and recorded in Phoenicia (whose inhabitants were referred to as Canaanites in the Bible) and Carthage by Hellenistic sources. 

Anna also mentions the Aztec ritual to Xipe Totec. The Aztecs performed several rituals to honor Xipe Totec, all usually performed in a yearly spring festival known as Tlacaxipehualiztli. During this festival, Aztec priests would flay the skin off of several people, including a man meant to impersonate the Flayed One, and culminated in a massive gladiatorial contest.

Something that they find on Megan's body and near Rob's corpse is the reverse pentagram, which is a symbol of Satanic worship. "A reversed pentagram, with two points projecting upwards, is a symbol of evil and attracts sinister forces because it overturns the proper order of things and demonstrates the triumph of matter over spirit. It is the goat of lust attacking the heavens with its horns, a sign execrated by initiates."

Anna mentions the Lindisfarne gospels. The Lindisfarne Gospels is an illuminated manuscript gospel book probably produced around the years 715–720 in the monastery at Lindisfarne, off the coast of Northumberland, which is now in the British Library in London.The Lindisfarne Gospels are presumed to be the work of a monk named Eadfrith, who became Bishop of Lindisfarne in 698 and died in 721.

The four people belonging to the circle gather in a neaby town, Alnmouth. Alnmouth is a coastal village in Northumberland, situated 4 miles east-south-east of Alnwick.