y. On reaching the door of Mademoiselle
Stangerson's apartment, it opened from a push given by the steward who
was waiting at the dinner-table. (Monsieur Stangerson had, for the last
three days, dined with his daughter in the drawing-room on the first
floor.) As the door remained open, we distinctly saw Mademoiselle
Stangerson, taking advantage of the steward's absence, and while her
father was stooping to pick up something he had let fall, pour the
contents of a phial into Monsieur Stangerson's glass.

CHAPTER XXI. On the Watch

The act, which staggered me, did not appear to affect Rouletabille much.
We returned to his room and, without even referring to what we had seen,
he gave me his final instructions for the night. First we were to go to
dinner; after dinner, I was to take my stand in the dark closet and wait
there as long as it was necessary--to look out for what might happen.

"If you see anything before I do," he explained, "you must let me know.
If the man gets into the 'right' gallery by any other way than the
'off-turning' gallery, you will see him before I shall, because you have
a view along the whole length of the 'right' gallery, while I can only
command a view of the 'off-turning' gallery. All you need do to let
me know is to undo the cord holding the curtain of the 'right' gallery
window, nearest to the dark closet. The curtain will fall of itself and
immediately leave a square of shadow where previously there had been a
square of light. To do this, you need but stretch your hand out of the
closet, I shall understand your signal perfectly."

"And then?"

"Then you will see me coming round the corner of the 'off-turning'
gallery."

"What am I to do then?"

"You will immediately come towards me, behind the man; but I shall
already be upon him, and shall have seen his face."

I attempted a feeble smile.

"Why do you smile? Well, you may smile while you have the chance, but I
swear you'll have no time for that a few hours from now.

"And if the man escapes?"

"So much the better," said Rouletabille, coolly, "I don't want to
capture him. He may take himself off any way he can. I will let
him go--after I have seen his face. That's all I want. I shall know
afterwards what to do so that as far as Mademoiselle Stangerson is
concerned he shall be dead to her even though he continues to live. If
I took him alive, Mademoiselle Stangerson and Robert Darzac would,
perhaps, never forgive me! And