secret purpose. This
purpose obsessed their minds throughout the operations; and what they
were looking for, under the furniture and in the cupboards, was one
thing and one thing alone: the crystal stopper. Therefore, if I want to
see clear ahead, I must first of all know what this means. It is certain
that, for some hidden reason, that mysterious piece of glass possesses
an incalculable value in their eyes. And not only in theirs, for, last
night, some one was bold enough and clever enough to enter my flat and
steal the object in question from me."

This theft of which he was the victim puzzled Lupin curiously.

Two problems, both equally difficult of solution, presented themselves
to his mind. First, who was the mysterious visitor? Gilbert, who enjoyed
his entire confidence and acted as his private secretary, was the only
one who knew of the retreat in the Rue Matignon. Now Gilbert was in
prison. Was Lupin to suppose that Gilbert had betrayed him and put the
police on his tracks? In that case, why were they content with taking
the crystal stopper, instead of arresting him, Lupin?

But there was something much stranger still. Admitting that they had
been able to force the doors of his flat--and this he was compelled to
admit, though there was no mark to show it--how had they succeeded in
entering the bedroom? He turned the key and pushed the bolt as he did
every evening, in accordance with a habit from which he never departed.
And, nevertheless--the fact was undeniable--the crystal stopper had
disappeared without the lock or the bolt having been touched. And,
although Lupin flattered himself that he had sharp ears, even when
asleep, not a sound had waked him!

He took no great pains to probe the mystery. He knew those problems too
well to hope that this one could be solved other than in the course of
events. But, feeling very much put out and exceedingly uneasy, he then
and there locked up his entresol flat in the Rue Matignon and swore that
he would never set foot in it again.

And he applied himself forthwith to the question of corresponding with
Vaucheray or Gilbert.

Here a fresh disappointment awaited him. It was so clearly understood,
both at the Sante Prison and at the Law Courts, that all communication
between Lupin and the prisoners must be absolutely prevented, that a
multitude of minute precautions were ordered by the prefect of police
and minutely observed by the lowest subordinates. Tried policemen,