and terrible phase. His luck was turning. It was no longer a matter of
attacking others, but of defending himself and saving the heads of his
two companions.

A little memorandum, which I have copied from one of the note-books
in which he often jots down a summary of the situations that perplex him,
will show us the workings of his brain:

"One definite fact, to begin with, is that Gilbert and Vaucheray
humbugged me. The Enghien expedition, undertaken ostensibly with the
object of robbing the Villa Marie-Therese, had a 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?