Pronouncing Valentine dead, d'Avrigny finds the glass inexplicably refilled with poison, proves it with nitric acid, and watches the guilty stepmother collapse.
Called at dawn by the nurse's screams, d'Avrigny pronounces the terrible words, 'Valentine is dead,' and Villefort's household flees in horror. But the doctor's eye falls on the girl's glass—which Madame de Villefort had emptied in the night, yet which now stands a third full of the same poisoned draught, as though 'a miracle from heaven' had preserved the proof. Dipping his finger and tasting, he declares 'it is no longer brucine,' fetches nitric acid from the sickroom's medicine closet, and drops it in: the liquid turns 'blood-red,' confirming the crime 'with the horror of a judge... mingled with the delight of a student making a discovery.' His gaze follows Héloïse as, overpowered, she staggers out and falls senseless on her floor; he sends the nurse to her with the icy words, 'Valentine de Villefort no longer requires help, since she is dead.' The physician who once concealed the poisonings now holds, in a glass of blood-red liquor, the incontrovertible proof of the poisoner's identity.
A grave physician of mature years, keen-eyed and implacable, his stern face lit with the mingled horror and triumph of discovery.
The doctor who proves the poisoning by chemical test and unmasks the stepmother's guilt.