He at once began love-making, and in spite of his ugliness succeeded in winning the heart of the lady to whom his colonel was attached; this led to such scandal that his father obtained a lettre de cachet, and the young scapegrace was imprisoned in the isle of Re.
His violent disposition now led him to quarrel with a country gentleman who had insulted his sister, and his semi-exile was changed by lettre de cachet into imprisonment in the Chateau d'If.
The affair ended by his escaping to Switzerland, where Sophie joined him; they then went to Holland, where he lived by hackwork for the booksellers; meanwhile Mirabeau had been condemned to death at Pontarlier for rapt et vol, and in May 1777 he was seized by the French police, and imprisoned by a lettre de cachet in the castle of Vincennes.
In the last year of his life he became acquainted with Mesmer, and published a Lettre sur le magnetisme animal.
It is agreed that the idea was suggested when Rousseau went to pay a visit to Diderot, who was in prison at Vincennes for his Lettre sur les aveugles.