On Friday, the 22nd of March, 1720, he went to the Rue Quincampoix, wishing, he said, to buy 100,000 ecus worth of shares, and for that purpose made an appointment with a stockbroker in a cabaret.  The stock-broker came there with his pocket-book and his shares; the Comte de Horn came also, accompanied, as he said, by two of his friends; a moment after, they all three threw themselves upon this unfortunate stock-broker; the Comte de Horn stabbed him several times with a poniard, and seized his pocket-book; one of his pretended friends (a Piedmontese named Mille), seeing that the stock-broker was not dead, finished the work.  At the noise they made the people of the house came, not sufficiently quick to prevent the murder, but in time to render themselves masters of the assassins, and to arrest them.  In the midst of the scuffle, the other cut-throat escaped, but the Comte de Horn and Mille were not so fortunate.  The cabaret people sent for the officers of justice, who conducted the criminals to the Conciergerie.  This horrible crime, committed in broad daylight, immediately made an immense stir, and several kinsmen of this illustrious family at once went to M. le Duc d’Orleans to beg for mercy; but the Regent avoided speaking to them as much as possible, and very rightly ordered full and prompt justice to be done.

At last, the relatives of Horn penetrated to the Regent:  they tried to make the Count pass for mad, saying even that he had an uncle confined in an asylum, and begging that he might be confined also.  But the reply was, that madmen who carried their madness to fury could not be got rid of too quickly.  Repulsed in this manner, they represented what an infamy it would be to their illustrious family, related to nearly all the sovereigns of Europe, to have one of its members tried and condemned.  M. le Duc d’Orleans replied that the infamy was in the crime, and not in the punishment.  They pressed him upon the honour the family had in being related to him.  “Very well, gentlemen,” said he, “I will divide the shame with you.”

The trial was neither long nor difficult.  Law and the Abbe Dubois, so interested in the safety of the stock-jobbers (without whom the paper must have fallen at once), supported M. le Duc d’Orleans might and main, in order to render him inexorable, and he, to avoid the persecutions he unceasingly experienced on the other side, left nothing undone in order to hurry the Parliament into a decision; the affair, therefore; went full speed, and it seemed likely that the Comte de Horn would be broken on the wheel.