As an independent scholar, he published many works on the English drama of the Stuart Restoration (1660–1688) and helped to organise and to promote the performance of plays from that period.

[2] Noted for his eccentric personality and interests, Summers became a popular figure in London high society first for his theatrical work and later for his History of Witchcraft and Demonology, published in 1926.

Its contents reflected the influence of the literary Decadent movement while showcasing Summers's own preoccupations with pederasty, medievalism, Catholic liturgy, and the occult.

[6] Summers dedicated that book to the writer Jacques d'Adelswärd-Fersen, who was notorious for having been convicted years earlier by a court in Paris of "inciting minors to debauchery".

[1]: 10  Summers's brief curacy ended under a cloud and he never proceeded to higher orders in the Anglican Church, apparently because of rumours of his interest in Satanism and allegations of sexual impropriety with young boys.

[3] Summers's interest in Satanism probably derived in part from his reading of the works of the French writer Joris-Karl Huysmans, particularly the novel Là-bas (1891), which includes an account of a Black Mass.

[8] In 1909, Summers converted to Catholicism and began studying for the Catholic priesthood at St John's Seminary, Wonersh,[2] receiving the clerical tonsure on 28 December 1910.

[2] Some sources claim that Summers then travelled to Continental Europe and was ordained by Cardinal Mercier in Belgium or by Archbishop Guido Maria Conforti in Italy.

[2] While employed as a schoolmaster and with the encouragement of Arthur Henry Bullen of the Shakespeare Head Press, Summers established himself as an independent scholar specializing on the dramatic literature of the Stuart Restoration.

[2] Summers helped to create a new society called "The Phoenix" that performed "old plays", including long neglected Restoration comedies, and which operated from 1919 to 1925 under the patronage of Lady Cunard and with the support of Sir Edmund Gosse.

[1]: 85 Several decades after his death, literary critic and historian Robert D. Hume characterized Montague Summers's scholarship on Restoration drama as pioneering and useful, but also as marred by sloppiness, eccentricity, uncritical deference to Edmund Gosse and other similar gentlemen-amateurs, and even occasional dishonesty.

[11] In his own day, Summers's credibility among university-based scholars was adversely impacted by the acrimonious public disputes in which he engaged with others working in the same field, such as Frederick S. Boas and Allardyce Nicoll.

[2] In the introduction to that book, Summers wrote: In the following pages I have endeavoured to show the witch as she really was – an evil liver: a social pest and parasite: the devotee of a loathly and obscene creed: an adept at poisoning, blackmail, and other creeping crimes: a member of a powerful secret organisation inimical to Church and State: a blasphemer in word and deed, swaying the villagers by terror and superstition: a charlatan and a quack sometimes: a bawd: an abortionist: the dark counsellor of lewd court ladies and adulterous gallants: a minister to vice and inconceivable corruption, battening upon the filth and foulest passions of the age.Summers expressed belief in the existence of demons, their role in possession and exorcism, and other preternatural phenomena associated with their activity.

[17] He considered that the testimonies according to which witches reached the location of their "sabbath" by magical flight were based on some delusion and argued that the "devil" reported to appear at such gatherings was an ordinary man in disguise, engaged in a burlesque of the ritual of the holy mass.

[1]: 50 The History of Witchcraft and Demonology sold well and attracted considerable attention in the press, with many reviewers expressing surprise that a 20th-century scholar had written as if the persons accused during the historical witch hunts had really been guilty of the crimes attributed to them.

In 1933, copies of Summers's translations of The Confessions of Madeleine Bavent and of Ludovico Maria Sinistrari's Demoniality were seized by the police due to their explicit accounts of sexual intercourse between humans and demons.

[2] Summers's work on the occult is notorious for his old-fashioned and eccentric writing style, his display of erudition, and his purported belief in the reality of some of the preternatural subjects he treats.

[17] According to historian Juliette Wood, Summers's concern with the macabre aspects of the supernatural has a very modern feel, and the links between vampires and satanic masses, so beloved of horror films and popular exorcisms, owe much to his particular body of work.

"[21] The prominent Catholic historian Jeffrey Burton Russell, a specialist in the religion of the European Middle Ages, wrote in 1972 that Summers' own works and his many editions and translations of classical witchcraft handbooks are marred by frequent liberties in translation, inaccurate references, and wild surmises; they are almost totally lacking in historical sense, for Summers saw witchcraft as a manifestation of the eternal and unchanging warfare between God and Satan.

Yet Summers was well steeped in the sources, and his insight that European witchcraft was basically a perversion of Christianity and related to heresy, rather than the survival of a pagan religion as the Murrayites claimed, was correct.

[2] These later writings draw extensively from earlier conspiracy theorists such as the French counter-revolutionary Abbé Augustin Barruel and the English Fascist Nesta Helen Webster.

His biographer, Father Brocard Sewell, paints the following portrait: During the year 1927, the striking and somber figure of the Reverend Montague Sommers in black soutane and cloak, with buckled shoes—a la Louis Quatorze—and shovel hat could often have been seen entering or leaving the reading room of the British Museum, carrying a large black portfolio bearing on its side a white label, showing in blood-red capitals, the legend 'VAMPIRES'.

Despite his conservative religiosity, Summers was an active member of the British Society for the Study of Sex Psychology, to which he contributed an essay on the Marquis de Sade in 1920.

Connolly privately mocked Summers in blank verse as "a sorcerer / a fruity unfrocked cleric of the Nineties / Like an old toad that carries in his head / The jewel of literature, a puffy satyr / That blends his Romish ritual with the filth / Scrawled on Pompeian pavement.

He collaborated with a number of student dramatic productions and became the object of much attention and gossip among Oxford University undergraduates, who regarded him as "a kind of clerical Doctor Faustus".

[28] According to Bernard Doherty, Thurston may have been concerned that Summers's writings on witchcraft could have been a "mystification" akin to the Taxil hoax of the 1890s, intended to bring ridicule upon the Catholic Church.

Both her only daughter and her husband had died insane, and she was convicted of fraud in 1934 for obtaining money to keep up her elegant lifestyle by writing deceptive begging letters to people whose names had appeared in the newspapers as recent beneficiaries of wills.

[31] The Catholic Bishop of Southwark, Peter Amigo, excommunicated Mrs. Greville-Nugent for allowing Summers to celebrate mass in the private oratory at Kingsley Dene, her home in Dulwich.

The Catholic rector of St Elizabeth of Portugal Church refused a public requiem mass, but conducted instead a private graveside ceremony.

An autobiography of Summers was published posthumously in 1980 as The Galanty Show, though it left much unrevealed about the author's life and dealt only with the literary side of his career.