of
it--"in which is the second key."

"That's quite clear," said the inspector.

"If, then, he did not make the attempt last night, when he had a clear
field--when the house was empty--he certainly will not make the attempt
now when we are warned, when the police are on the spot, and the house
is surrounded. The idea is childish, gentlemen"--he leaned against the
door of the safe--"absolutely childish, but Guerchard is mad on this
point; and I foresee that his madness is going to hamper us in the most
idiotic way."

He suddenly pitched forward into the middle of the room, as the door of
the safe opened with a jerk, and Guerchard shot out of it.

"What the devil!" cried M. Formery, gaping at him.

"You'd be surprised how clearly you hear everything in these
safes--you'd think they were too thick," said Guerchard, in his gentle,
husky voice.

"How on earth did you get into it?" cried M. Formery.

"Getting in was easy enough. It's the getting out that was awkward.
These jokers had fixed up some kind of a spring so that I nearly shot
out with the door," said Guerchard, rubbing his elbow.

"But how did you get into it? How the deuce DID you get into it?" cried
M. Formery.

"Through the little cabinet into which that door behind the safe opens.
There's no longer any back to the safe; they've cut it clean out of
it--a very neat piece of work. Safes like this should always be fixed
against a wall, not stuck in front of a door. The backs of them are
always the weak point."

"And the key? The key of the safe upstairs, in my bedroom, where the
coronet is--is the key there?" cried M. Gournay-Martin.

Guerchard went back into the empty safe, and groped about in it. He
came out smiling.

"Well, have you found the key?" cried the millionaire.

"No. I haven't; but I've found something better," said Guerchard.

"What is it?" said M. Formery sharply.

"I'll give you a hundred guesses," said Guerchard with a tantalizing
smile.

"What is it?" said M. Formery.

"A little present for you," said Guerchard.

"What do you mean?" cried M. Formery angrily.

Guerchard held up a card between his thumb and forefinger and said
quietly:

"The card of Arsene Lupin."

CHAPTER XIV

GUERCHARD PICKS UP THE TRUE SCENT

The millionaire gazed at the card with stupefied eyes, the inspector
gazed at it with extreme intelligence, the Duke gazed at it with
interest, and M. Formery gazed at it with extreme disgust.

"It's