“Yes,” snapped Smith, sitting suddenly upright—­“yes!  You experience this?  Good!  You are happily sensitive to this type of impression, Petrie, and therefore quite as useful to me as a cat is useful to a physical investigator.”

He laughed in his quick, breezy fashion.

“You will appreciate my meaning,” he added; “therefore I offer no excuse for the analogy.  Of course, the circumstances, as we know them, may be responsible for this consciousness of unrest.  We are neither of us likely to forget the attempt upon the life of Sir Lionel Barton two years ago or more.  Our attitude toward sudden illness is scarcely that of impartial observers.”

“I suppose not,” I admitted, glancing yet again at the still vacant doorway by the foot of the stairs, which now the twilight was draping in mysterious shadows.

Indeed, our position was a curious one.  A welcome invitation from our old friend, Sir Lionel Barton, the world-famous explorer, had come at a time when a spell of repose, a glimpse of sea and awakening countryside, and a breath of fair, untainted air were very desirable.  The position of Karamaneh, who accompanied us, was sufficiently unconventional already, but the presence of Mrs. Oram, the dignified housekeeper, had rendered possible her visit to this bachelor establishment.  In fact it was largely in the interests of the girl’s health that we had accepted.

On our arrival at Graywater Park we had learnt that our host had been stricken down an hour earlier by sudden illness.  The exact nature of his seizure I had thus far been unable to learn; but a local doctor, who had left the Park barely ten minutes before our advent, had strictly forbidden visitors to the sick-room.  Sir Lionel’s man, Kennedy, who had served him in many strange spots in the world, was in attendance.

So much we had gathered from Homopoulo, the Greek butler (Sir Lionel’s household had ever been eccentric).  Furthermore, we learned that there was no London train that night and no accommodation in the neighboring village.

“Sir Lionel urgently requests you to remain,” the butler had assured us, in his flawless, monotonous English.  “He trusts that you will not be dull, and hopes to be able to see you to-morrow and to make plans for your entertainment.”

A ghostly, gray shape glided across the darkened hall—­and was gone.  I started involuntarily.  Then remote, fearsome, came muted howling to echo through the ancient apartments of Graywater Park.  Nayland Smith laughed.

“That was the civet cat, Petrie!” he said.  “I was startled, for a moment, until the lamentations of the leopard family reminded me of the fact that Sir Lionel had transferred his menagerie to Graywater!”