In 1903, a scandal involving school pupils made d'Adelswärd persona non grata in the salons of Paris and dashed his marriage plans.

On his father's side, his family can be traced back to Baron Georges Axel d'Adelswärd, a Swedish officer who was captured by the French in 1793 and imprisoned in Longwy.

D'Adelswärd went to school in Paris and studied briefly there at the École libre des sciences politiques, and afterward at the University of Geneva.

D'Adelswärd was arrested on 9 July by Octave Hamard, chief of the Paris police, and his deputy Blot by order of Charles de Valles, pretrial judge.

The newspapers and magazines published alleged details of d'Adelswärd's and Hamelin's orgies, which they called messes noires (Black Masses), in their homes twice a week, with youngsters from the upper classes, mostly recruited from the Lycée Carnot and the Chaptal, Condorcet, Janson-deSailly, and Saint-Joseph-des-Tuileries schools.

According to Peyrefitte, the scandal started with a failed blackmail attempt by d'Adelswärd's former servant, demanding 100,000 francs in return for his silence.

Will Ogrinc reported that, after investigating the French National Archives in 2003, he did not come across any documents about the failed blackmail attempt by d'Adelswärd's former valet and that it was probably invented by Peyrefitte.

His aunt Jeanne d'Adelswärd and former guardian Viscount Audoin de Dampierre employed Edgar Demange, a lawyer who previously defended Alfred Dreyfus, in his defence.

The "entertainments" had been attended by the cream of Parisian society, including some Catholic priests and the writer Achille Essebac.

According to Will Ogrinc, the court limited the case to "inciting minors to debauchery" because of illegal conduct between boys and two young men in their twenties, preventing implications against older participants.

The island had already attracted other homosexual or bisexual visitors, such as Christian Wilhelm Allers, Somerset Maugham, E. F. Benson, Lord Alfred Douglas, Robert Ross, Oscar Wilde, Friedrich Alfred Krupp, Norman Douglas, and Compton and Faith Mackenzie; and attracted many others during d'Adelswärd's stay.

He stayed originally at the Grand Hotel Quisisana and then bought land at the top of a hill in the northeast of the island, close to where the Roman emperor Tiberius had built his Villa Jovis two millennia earlier.

At some point after his return, he had to flee Capri temporarily, since some islanders blamed d'Adelswärd for a local worker's accidental death during the construction of Villa Lysis.

In the atrium a marble stairway with wrought-iron balustrade leads to the first floor, where there are bedrooms with panoramic terraces, and a dining room.

D'Adelswärd published his novel about Capri Et le feu s'éteignit sur la mer… ('And the fire was smothered by the sea') in 1909.

Roberto Ciuni reports that the Communal Council of Capri decided to pursue d'Adelswärd's expulsion from the island at its formal meeting on 16 September 1909.

"[7]Local authorities used the parties d'Adelswärd threw to celebrate Cesarini's army enlistment and twentieth birthday as an additional reason for expelling him from the island.

The marquis summoned d'Adelswärd to Naples and presented him with two options – either to leave Italy voluntarily or be expelled officially.

He mostly spent his days without leaving the villa, either working in his study or using opium in the smoking room, which was called his Opiarium by the Naples newspaper Il Mattino.

In 1920, d'Adelswärd met fifteen-year-old Corrado Annicelli, son of a notary from Sorrento, who came for a vacation to Capri with his parents.

He spent the rest of his life based in Capri, and died there in 1923 – allegedly by suicide achieved through drinking a cocktail of champagne and cocaine.

Lord Lyllian, published in 1905, is one of d'Adelswärd's more important novels, satirizing the scandal around himself in Paris, with touches of the Oscar Wilde affair thrown in for good measure.

Revue Mensuelle d'Art Libre et de Critique (1909)[9] was d'Adelswärd's short-lived attempt at publishing a monthly literary journal.

It was a periodical of a luxurious kind, each issue printed on several sorts of deluxe paper, with contributions by well-known authors, like Colette, Henry Gauthier-Villars, Laurent Tailhade, Josephin Peladan, Marcel Boulestin, Maxim Gorky, Georges Eekhoud, Achille Essebac, Claude Farrère, Anatole France, Filippo Tommaso Marinetti, Henri Barbusse, Jean Moréas and Arthur Symons.

In each issue, as is clear from d'Adelswärd's letters to Georges Eekhoud,[10] a homosexual element was carefully introduced: a poem, an article, or a hint in the magazine's serial Les Fréquentations de Maurice by Boulestin.

In its 'gay' content it trod similar ground to that of the German journal, Der Eigene, published between 1896 and 1931 by Adolf Brand.