efore by an
old client, who, at the last moment, had sent a _petit bleu_ to say that he
had changed his plans and would not require the room. The _petit bleu_ did
not arrive until after the crime was discovered, so the room remained
empty. More than that, the door was locked.

"Locked on the outside?"

"Yes."

"With the key in the lock?"

"Yes."

"Then anyone coming along the corridor might have turned the key and
entered Number Seven?"

"It is possible," admitted M. Gritz, "but very improbable. The room was
dark, and an ordinary person seeing a door locked and a room dark----"

"We are not talking about an ordinary person," retorted the detective, "we
are talking about a murderer. Come, we must look into this," and he led the
way down the corridor, nodding to the policeman outside Number Six and
stopping at the next door, the last in the line, the door to Number Seven.

"You know I haven't been in _there_ yet." He glanced toward the adjoining
room of the tragedy, then, turning the key in Number Seven, he tried to
open the door.

"Hello! It's locked on the inside, too!"

"_Tiens!_ You're right," said Gritz, and he rumpled his scanty locks in
perplexity.

"Some one has been inside, some one may be inside now."

The proprietor shook his head and, rather reluctantly, went on to explain
that Number Seven was different from the other private rooms in this, that
it had a separate exit with separate stairs leading to an alleyway between
the hotel and a wall surrounding it. A few habitues knew of this exit and
used it occasionally for greater privacy. The alleyway led to a gate in the
wall opening on the Rue Marboeuf, so a particularly discreet couple, let us
say, could drive up to this gate, pass through the alleyway, and then, by
the private stairs, enter Number Seven without being seen by anyone,
assuming, of course, that they had a key to the alleyway door. And they
could leave the restaurant in the same unobserved manner.

As Coquenil listened, his mouth drew into an ominous thin line and his deep
eyes burned angrily.

"M. Gritz," he said in a cold, cutting voice, "you are a man of
intelligence, you must be. This crime was committed last night about nine
o'clock; it's now half past three in the morning. Will you please tell me
how it happens that this fact _of vital importance_ has been concealed from
the police for over six hours?"

"Why," stammered the other, "I--I don't know."

"Are you trying to sh