g else upon the paper, but
Duvall realized that he held in his hand the key of the cipher.

At once Monsieur de Grissac's agitation, the servant Noel's death,
Hartmann's persecution of him, became clear. Evidently there were
documents, somewhere, of some nature, which this cipher made
intelligible and which, without it, were proof against all attempts to
read them. What were these documents? Were they in Hartmann's hands?
These questions, he knew, could not be answered now.

Immediately the question rose in his mind: What should he do next? By
destroying the tiny slip of paper, he could render the snuff box
valueless. Without the key, no one could use it with success. But, the
key once destroyed, how could Monsieur de Grissac himself read the
documents, for the preparing of which it had been utilized? Possibly, if
Hartmann had such documents, they were but copies, obtained through the
corruption of some clerk, while the originals remained in De Grissac's
possession. For these reasons he dared not destroy the cipher, at least
until all other means of escape had been exhausted. Then he realized, in
a flash, that if he proposed to utilize the return of the snuff box as a
means of obtaining his freedom, he could not hope to do so, if the key
was removed. Doubtless Hartmann knew of its existence. In some way he
had learned, possibly through the murdered man Noel, that the box
contained such a key, and would examine it, and satisfy himself that it
had not been removed, before he would allow him to leave the place. This
would inevitably result in his being searched, and the key, concealed
about his person, found. He stood in an agony of doubt, wondering which
alternative he should take.

His reflections were rudely disturbed by the sound of footsteps in the
corridor outside the door. In a moment he had replaced the tiny bit of
paper in the recess beneath the cross, slid the latter back into place,
and thrust the box beneath a mass of straw which lay on top of the
packing case against which he had been leaning. Then he turned toward
the door and had barely time to hurl the opera hat into a dark corner,
when the door opened, and Hartmann appeared on the threshold.

CHAPTER XIX

It was not until early in the afternoon that Grace was able to
accomplish anything toward carrying out the instructions which young
Lablanche had given her with respect to the phonograph. On her return to
Dr. Hartmann's from her expedition to