On hearing of Mme. de Lamotte's contemplated visit to Paris, Derues was filled with alarm. If she were living free and independent in Paris she might find out the truth about the real state of his affairs, and then good-bye to Buisson-Souef and landed gentility! No, if Mme. de Lamotte were to come to Paris, she must come as the guest of the Derues, a pleasant return for the hospitality accorded to the grocer at Buisson-Souef. The invitation was given and readily accepted; M. de Lamotte still had enough confidence in and liking for the Derues to be glad of the opportunity of placing his wife under their roof. And so it was that on December 16, 1776, Mme. de Lamotte arrived at Paris and took up her abode at the house of the Derues in the Rue Beaubourg Her son she placed at a private school in a neighbouring street. To Derues there was now one pressing and immediate problem to be solved--how to keep Buisson-Souef as his own without paying for it? To one less sanguine, less daring, less impudent and desperate in his need, the problem would have appeared insoluble. But that was by no means the view of the cheery and resourceful grocer. He had a solution ready, well thought out and bearing to his mind the stamp of probability. He would make a fictitious payment of the purchase-money to Mme. de Lamotte. She would then disappear, taking her son with her. Her indiscretion in having been the mistress of de Lamotte before she became his wife, would lend colour to his story that she had gone off with a former lover, taking with her the money which Derues had paid her for Buisson-Souef. He would then produce the necessary documents proving the payment of the purchase-money, and Buisson-Souef would be his for good and all. The prime necessity to the success of this plan was the disappearance, willing or unwilling, of Mme. de Lamotte and her son. The former had settled down quite comfortably beneath the hospitable roof of the Derues, and under the soothing influence of her host showed little vigour in pressing him for the money due to herself and her husband. She had already spent a month in quietly enjoying Paris and the society of her friends when, towards the end of January, 1770, her health and that of her son began to fail. Mme. de Lamotte was seized with sickness and internal trouble. Though Derues wrote to her husband that his wife was well and their business was on the point of conclusion, by the 30th of January Mme. de Lamotte had taken to her bed, nursed and physicked by the ready Derues. On the 31st the servant at the Rue Beaubourg was told that she could go to her home at Montrouge, whither Derues had previously sent his two children. Mme. Derues, who was in an interesting condition, was sent out for an hour by her husband to do some shopping. Derues was alone with his patient.