There was another pause; this time it was Pendleton who broke the silence.

“As you say,” spoke he, in a strange, throaty sort of tone, “she has not been quite frank.  Take all the circumstances together and they seem to point—­”

He paused as though quite unable to finish.  Ashton-Kirk laid a hand upon his shoulder.

“Imagination is a thing that is vitally necessary in this sort of work,” said he.  “But it must be held in check by reason.  The great trouble with an amateur is that he reasons up to a certain point; then he allows his imagination to take a long leap toward a result.  The upshot is that his results have seldom anything to support them.  The correct method, I think, is to allow the imagination to scurry ahead in the way that is natural to it; but reason must follow close behind, proving each step of the way.  To be sure, you may have theories, hypotheses, ideas without end, but you must never take them for granted.  Select each in its turn, place it in a tube as the chemist does, add a few drops of reason, and you may produce a fact.  It is the only way to go about it.  Once a man becomes fixed in a belief, be there ever so little foundation for it, his mind stops revolving the subject; further procedure is hopeless.”

“I understand all that well enough,” said Pendleton.  “But,” and he waved his hand toward the house, “what does this mean?”

“I don’t know,” said Ashton-Kirk.  “And neither do you.  So—­that being the case—­there is but one thing to do—­find out.”

They gazed toward the window once more, Miss Vale had apparently mastered the contents of the paper, and was now engaged in writing rapidly.  As the young men watched, she stopped, read carefully what she had written, and then handed it to Locke.  The mute carried the paper to the light, and holding it very near to his eyes read it with much attention; then he tore it into strips, placed it upon the red coals of a stove which stood near him and watched it burn.  Facing Miss Vale, his fingers began to fly rapidly in intricate signs.  This only lasted a moment, however; for he stopped, gestured passionately, seized a pad of paper and began to write.

While he was thus engaged, Ashton-Kirk said to Pendleton in a low tone: 

“Remain here for a moment.”

Then slowly, carefully, the investigator made his way toward the window through which Miss Vale and Locke were to be seen.

Heavy beams of light shot across the ground from the windows; but here and there were trails of shadow.  He clung to these until he had reached the shelter of the walls; then to Pendleton’s amazement he stepped directly in front of the window through which the two were to be seen, rapped smartly upon the glass, and remained standing in full view, of the two in the room.

[Illustration:  HE RAPPED SMARTLY ON THE WINDOW]