f you."

"Monsieur de Grissac," asked Duvall, his face white, "had I destroyed
the box, or even only the key, could you have read these documents
yourself?"

The Ambassador gazed at him, puzzled for a moment. "Certainly not,
monsieur," he replied. "I could no more have solved the cipher than they
could. It was for that reason that I was forced to carry the key about
with me. But it would have been infinitely better, had the documents
never again been read, than to have them read by our enemies."

Without making any reply, Duvall placed his hand in his pocket and drew
out, between his thumb and forefinger, a tiny white pellet, no larger
than the head of a match. "You are no doubt acquainted, Monsieur de
Grissac," he said, coolly, "with your own handwriting."

"My handwriting! Naturally. What of it?" He went toward the detective,
an eager look in his face. Lefevre, Dufrenne, and Grace also crowded
about, their expressions showing the interest which Duvall's questions
had aroused.

The detective began to unroll the little white pellet with the utmost
deliberation. It presently became a tiny strip of tissue paper, not over
two and a half inches long, upon which was written a series of numbers.
"Is that, then, your handwriting, monsieur?" he inquired carelessly, as
he placed the strip of paper in De Grissac's trembling hand.

"_Mon Dieu!_ The key!" fairly shouted the Ambassador, as his eyes fell
upon the bit of paper. "Monsieur Duvall, what does this mean?"

"It means, monsieur," replied the detective, coolly, "that while I was
left alone in the room downstairs, I tore off the lower half of your
key, which luckily, was a sufficient width to enable me to do so, and
with a fountain pen I had in my pocket, wrote upon this second slip of
paper a series of numbers taken at random. This series I placed in the
secret recess in the box. I do not think it will prove of much use to
our friends in Brussels."

"Duvall!" cried Lefevre, rushing forward with outstretched hands.
"Forgive me--forgive me!" He was not quick enough, however, to forestall
Grace, who with one cry of happiness had flung herself into her
husband's arms. "Richard!" she cried, and then sank sobbing but happy
upon his breast.

Monsieur Lefevre seized his assistant by the arm and began to shake his
hand in a way which almost threatened to dislocate the young man's
shoulder. "My boy," he cried, laughing and crying at the same time,
"forgive me--forgive me. I