Mademoiselle Stangerson would have died of strangulation.
"The affair as reported in the 'Matin,'" said Rouletabille eagerly, "seems to me more and more inexplicable. Can you tell me, Monsieur, how many openings there are in the pavilion? I mean doors and windows."
"There are five," replied Monsieur de Marquet, after having coughed once or twice, but no longer resisting the desire he felt to talk of the whole of the incredible mystery of the affair he was investigating. "There are five, of which the door of the vestibule is the only entrance to the pavilion,—a door always automatically closed, which cannot be opened, either from the outer or inside, except with the two special keys which are never out of the possession of either Daddy Jacques or Monsieur Stangerson. Mademoiselle Stangerson had no need for one, since Daddy Jacques lodged in the pavilion and because, during the daytime, she never left her father. When they, all four, rushed into The Yellow Room, after breaking open the door of the laboratory, the door in the vestibule remained closed as usual and, of the two keys for opening it, Daddy Jacques had one in his pocket, and Monsieur Stangerson the other. As to the windows of the pavilion, there are four; the one window of The Yellow Room and those of the laboratory looking out on to the country; the window in the vestibule looking into the park."
"It is by that window that he escaped from the pavilion!" cried Rouletabille.
"How do you know that?" demanded Monsieur
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