“We’ll see later how he got away from The Yellow Room,” replied Rouletabille, “but he must have left the pavilion by the vestibule window.” “Once more,—how do you know that?” “How? Oh, the thing is simple enough! As soon as he found he could not escape by the door of the pavilion his only way out was by the window in the vestibule, unless he could pass through a grated window. The window of The Yellow Room is secured by iron bars, because it looks out upon the open country; the two windows of the laboratory have to be protected in like manner for the same reason. As the murderer got away, I conceive that he found a window that was not barred,—that of the vestibule, which opens on to the park,—that is to say, into the interior of the estate. There’s not much magic in all that.” “Yes,” said Monsieur de Marquet, “but what you have not guessed is that this single window in the vestibule, though it has no iron bars, has solid iron blinds. Now these iron blinds have remained fastened by their iron latch; and yet we have proof that the murderer made his escape from the pavilion by _that_ window! Traces of blood on the inside wall and on the blinds as well as on the floor, and footmarks, of which I have taken the measurements, attest the fact that the murderer made his escape that way. But then, how did he do it, seeing that the blinds remained fastened on the inside? He passed through them like a shadow. But what is more bewildering than all is that it is impossible to form any idea as to how the murderer got out of The Yellow Room, or how he got across the laboratory to reach the vestibule! Ah, yes, Monsieur Rouletabille, it is altogether as you said, a fine case, the key to which will not be discovered for a long time, I hope.” “You hope, Monsieur?” Monsieur de Marquet corrected himself. “I do not hope so,—I think so.” “Could that window have been closed and refastened after the flight of the assassin?” asked Rouletabille. “That is what occurred to me for a moment; but it would imply an accomplice or accomplices,—and I don’t see—” After a short silence he added:— “Ah—if Mademoiselle Stangerson were only well enough to-day to allow of her being questioned!” Rouletabille following up his thought, asked:— “And the attic?—There must be some opening to that?” “Yes; there is a window, or rather skylight, in it, which, as it looks out towards the country, Monsieur Stangerson has had barred, like the rest of the windows. These bars, as in the other windows, have remained intact, and the blinds, which naturally open inwards, have not been unfastened. For the rest, we have not discovered anything to lead us to suspect that the murderer had passed through the attic.” “It seems clear to you, then, Monsieur, that the murderer escaped—nobody knows how—by the window in the vestibule?” “Everything goes to prove it.” “I think so, too,” confessed Rouletabille gravely. After a brief silence, he continued:—