ease let me have a formal receipt and quittance. I want you
to understand that my decision on the matter is final. I regret that I
am obliged to back out at the last moment, but no doubt you will be able
to proceed without my help."

The letter was in handwriting, and had not been press-copied. Larssen
noted that point at once with satisfaction. But the letter itself gave
him uneasiness. It explained nothing of Matheson's motives. From the
'phone conversation with Olive, it was clear that she had no suspicion
that her husband wanted to withdraw from the Hudson Bay deal. In fact,
she had asked anxiously if anything had gone wrong with the scheme. Sir
Francis Letchmere might of course be closer in Matheson's business
confidence, and that was one of the reasons for travelling to Monte
Carlo and talking to him face to face.

But with his keen intuitive sense, Lars Larssen felt that the
explanation was in some way connected with this mysterious John Riviere.
It was imperative to get in touch with the man.

Where was Riviere? Was there nobody who could throw light on his
whereabouts? His jaw tightened as he began to chew on the problem. Paris
is too big a city in which to hunt for a mere name.

After thanking the manager, Larssen withdrew from the room. Passing
through the outer office, he was addressed by the other of the two
clerks, a young Frenchman.

"Monsieur," said he in French, "here is a point which perhaps will be of
service. I am at the window when Monsieur Riviere arrives _en
taxi-auto_. On the _imperiale_ I see a portmanteau. Doubtless Monsieur
Riviere journeys away from Paris."

"Did you note the number of the cab?"

The young Frenchman made a gesture of sympathetic negation. There had
been no reason to look at the number, even if he could have read it from
a window on the second story.

"Thanks," said Larssen, but the information seemed at first sight
valueless. A man takes an unknown cab from an unknown house in an
unknown suburb to an unknown terminus, when he buys a ticket for an
unknown destination. Sheer waste of energy to hunt for a needle in that
haystack!

Yet his bulldog mind would not let go of the problem. Presently he had
found a new avenue of approach to it. If Riviere had travelled away from
Paris on the evening of the 15th, probably he stayed that night or the
next day at some hotel. There he would have to fill in his name, etc.,
in the hotel register according to the strict requirement