What does Marguerite think caused her husband to stop loving her

Percy believes that his wife denounced the Marquis de St. Cyr, something that killed his love for her.

‘That I denounced the Marquis de St. Cyr, you mean, to the tribunal that ultimately sent him and all his family to the guillotine? Yes, he does know…. . I told him after I married him….’ ‘You told him all the circumstances—which so completely exonerated you from any blame?’ ‘It was too late to talk of ‘circumstances’; he heard the story from other sources; my confession came too tardily, it seems. I could no longer plead extenuating circumstances: I could not demean myself by trying to explain—‘ ‘And?’ ‘And now I have the satisfaction, Armand, of knowing that the biggest fool in England has the most complete contempt for his wife.’

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Blakeney was slow-witted, he would not listen to ‘circumstances,’ he only clung to facts, and these had shown him Lady Blakeney denouncing a fellow man to a tribunal that knew no pardon: and the contempt he would feel for the deed she had done, however unwittingly, would kill that same love in him, in which sympathy and intellectuality could never had a part.