“For my father?”

“Yes.”

“But how could a dose prepared for M. Noirtier poison Madame de Saint-Méran?”

“Nothing is more simple. You know poisons become remedies in certain diseases, of which paralysis is one. For instance, having tried every other remedy to restore movement and speech to M. Noirtier, I resolved to try one last means, and for three months I have been giving him brucine; so that in the last dose I ordered for him there were six grains. This quantity, which is perfectly safe to administer to the paralyzed frame of M. Noirtier, which has become gradually accustomed to it, would be sufficient to kill another person.”