During the journey Madame de Brinvilliers was escorted by the Marshal d'Estrades in person as far as Huy, and from Huy to Rocroi by the troops of Monsieur de Montal. The prisoner's character displayed itself in all its untamed energy. Locked up at Maestricht, she suggested to Antoine Barbier, an archer of the guard who had won her confidence, to make a gag and a rope-ladder: the gag was for Desgrez and the rope-ladder for her own escape. She promised Barbier a thousand pistoles. At other times she urged him to help her throttle Desgrez, kill the _valet de chambre_, detach the two leading horses from the coach, take the documents, the casket with her confession, and another important paper, and burn them all, for which purpose he was to carry a lighted match.
She wrote to former servants who remained faithful to her, and actually succeeded in getting letters delivered to them, for they endeavoured to rescue her, and tried to bribe her guardians.
She persisted in the plan she had devised in regard to the accusation under which Pennautier lay. She asked Barbier for ink to write to him; he gave her some, and feigned to have despatched the letter. And when he asked her if Pennautier was one of her friends, 'Yes, yes,' she replied, 'and he is as much interested in my safety as I am myself.' Another time she said: 'He must be much more frightened than I am. I have been questioned about him, but I have said nothing, and have too much feeling to charge him: half of the aristocracy are involved too, and I should ruin them all if I spoke.' This she repeated several times.
At Mézières the marchioness met Denis de Palluau, a Parlement counsellor, whom the court had deputed to put her through a first interrogation. Corbinelli, the friend of Madame de Sévigné, wrote to Madame de Grignan: 'The king has required the Parlement to depute Palluau, counsellor in the High Court, to go to Rocroi, where he is to interrogate the Brinvilliers, because they don't wish to wait till she arrives here, where the whole bar is connected with the poor criminal.'
The first examination to which Palluau subjected the marchioness is dated Mézières, April 17, 1676. The prisoner took refuge in systematic denials.