“And tomorrow, unless I am mistaken, is full moon,” said the doctor suddenly, watching the other’s face for the effect of his apparently careless words.

Colonel Wragge gave an uncontrollable start, and his face for the first time showed unmistakable pallor.

“What in the world—–?” he began, his lip quivering.

“Only that I am beginning to see light in this extraordinary affair,” returned the other calmly, “and, if my theory is correct, each month when the moon is at the full should witness an increase in the activity of the phenomena.”

“I don’t see the connection,” Colonel Wragge answered almost savagely, “but I am bound to say my diary bears you out.”  He wore the most puzzled expression I have ever seen upon an honest face, but he abhorred this additional corroboration of an explanation that perplexed him.

“I confess,” he repeated, “I cannot see the connection.”

“Why should you?” said the doctor, with his first laugh that evening.  He got up and hung the map upon the wall again.  “But I do—­because these things are my special study—­and let me add that I have yet to come across a problem that is not natural, and has not a natural explanation.  It’s merely a question of how much one knows—­and admits.”

Colonel Wragge eyed him with a new and curious respect in his face.  But his feelings were soothed.  Moreover, the doctor’s laugh and change of manner came as a relief to all, and broke the spell of grave suspense that had held us so long.  We all rose and stretched our limbs, and took little walks about the room.

“I am glad, Dr. Silence, if you will allow me to say so, that you are here,” he said simply, “very glad indeed.  And now I fear I have kept you both up very late,” with a glance to include me, “for you must be tired, and ready for your beds.  I have told you all there is to tell,” he added, “and tomorrow you must feel perfectly free to take any steps you think necessary.”

The end was abrupt, yet natural, for there was nothing more to say, and neither of these men talked for mere talking’s sake.

Out in the cold and chilly hall he lit our candles and took us upstairs.  The house was at rest and still, every one asleep.  We moved softly.  Through the windows on the stairs we saw the moonlight falling across the lawn, throwing deep shadows.  The nearer pine trees were just visible in the distance, a wall of impenetrable blackness.

Our host came for a moment to our rooms to see that we had everything.  He pointed to a coil of strong rope lying beside the window, fastened to the wall by means of an iron ring.  Evidently it had been recently put in.

“I don’t think we shall need it,” Dr. Silence said, with a smile.

“I trust not,” replied our host gravely.  “I sleep quite close to you across the landing,” he whispered, pointing to his door, “and if you—­if you want anything in the night you will know where to find me.”