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 be
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 dis