Rouletabille was quick enough to note the bad impression he had made, for, turning to the President, he said: "And now we come to the explanation of the Mystery of The Yellow Room!" A movement of chairs in the court with a rustling of dresses and an energetic whispering of "Hush!" showed the curiosity that had been aroused.
"It seems to me," said the President, "that the Mystery of The Yellow Room, Monsieur Rouletabille, is wholly explained by your hypothesis.
Frederic Larsan is the explanation.

We have merely to substitute him for Monsieur Robert Darzac.

Evidently the door of The Yellow Room was open at the time Monsieur Stangerson was alone, and that he allowed the man who was coming out of his daughter's chamber to pass without arresting him--perhaps at her entreaty to avoid all scandal." "No, Monsieur President," protested the young man.

"You forget that, stunned by the attack made on her, Mademoiselle Stangerson was not in a condition to have made such an appeal.

Nor could she have locked and bolted herself in her room.