>>11370229 lb
It's close to Feast Day, or the Summer Solstice. I am not sure if Martin used the actual dates in his book, so I shall check.
"In his novel, Windswept House, which Fr. Martin always maintained was 90 percent fact and 10 percent fiction, the opening chapter describes this Mass."
Black Mass Within the Vatican:
"Martin, who died in 1996, says that at the height of the Second Vatican Council in Rome, there was a ceremony to enthrone Lucifer in the Vatican (and the Chair of Peter). The church in question, Saint Paul’s chapel within the Vatican walls, hosted a very different rite of Mass on January 29 (Not sure about this date.), 1963, just one week after the election of Pope Paul VI. (Years later, according to Fr. Martin, Pope Paul VI would write a note to his successor, John Paul II, and tell him of this ceremony.) Paul VI is also famous for his statement, "The smoke of Satan has entered the sanctuary."
http://philadelphiafreepress.com/the-black-mass-within-vatican-walls-p2368-1.htm
"There has been barely time since the papal Conclave had ended, June 21 1963, with the election of Paul VI, for the complex arrangement to be readied; but Supreme Tribunal had decided there could be no more perfect date for the Enthronement of the Prince than the feast day of the twin princes of the Citadel: St. Peter and Paul. And there could be no more perfect place than the Chapel of St.Paul itself, situated as it was so near to the Apostolic Palace."
https://padrepioandchiesaviva.com/uploads/Satana_in._Vaticano_en_OK-final.pdf
I will read some more and see. I read Windswept House several years ago so the details are murky.