Larsan's true motive. The explanation he had given had evidently
been unsatisfactory. 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. You must also remember
that Monsieur Stangerson has sworn that the door was not open."

"That, however, is the only way in which it can be explained. The
Yellow Room was as closely shut as an iron safe. To use your own
expression, it was impossible for the murderer to make his escape
either naturally or supernaturally. When the room was broken into
he was not there! He must, therefore, have escaped."