I was feeling underneath the boat, with a sense of absurdity that McWhirter put into words.  “I only hope,” he said, “that the watchman does not wake up now and see us.  He’d be justified in filling us with lead, or putting us in straitjackets.”

But I had discovered something.

“Mac,” I said, “some one has been at this boat within the last few minutes.”

“Why?”

“Take your revolver and watch the deck.  One of the barecas—­”

“What’s that?”

“One of the water-barrels has been upset, and the plug is out.  It is leaking into the boat.  It is leaking fast, and there’s only a gallon or so in the bottom!  Give me the light.”

The contents of the boat revealed the truth of what I had said.  The boat was in confusion.  Its cover had been thrown back, and tins of biscuit, bailers, boathooks and extra rowlocks were jumbled together in confusion.  The barecas lay on its side, and its plug had been either knocked or drawn out.

McWhirter was for turning to inspect the boat; but I ordered him sternly to watch the deck.  He was inclined to laugh at my caution, which he claimed was a quality in me he had not suspected.  He lounged against the rail near me, and, in spite of his chaff, kept a keen enough lookout.

The barecas of water were lashed amidships.  In the bow and stern were small air-tight compartments, and in the stern was also a small locker from which the biscuit tins had been taken.  I was about to abandon my search, when I saw something gleaming in the locker, and reached in and drew it out.  It appeared to be an ordinary white sheet, but its presence there was curious.  I turned the light on it.  It was covered with dark-brown stains.

Even now the memory of that sheet turns me ill.  I shook it out, and Mac, at my exclamation, came to me.  It was not a sheet at all, that is, not a whole one.  It was a circular piece of white cloth, on which, in black, were curious marks—­a six-pointed star predominating.  There were others—­a crescent, a crude attempt to draw what might be either a dog or a lamb, and a cross.  From edge to edge it was smeared with blood.

Of what followed just after, both McWhirter and I are vague.  There seemed to be, simultaneously, a yell of fury from the rigging overhead, and the crash of a falling body on the deck near us.  Then we were closing with a kicking, biting, screaming thing, that bore me to the ground, extinguishing the little electric flash, and that, rising suddenly from under me, had McWhirter in the air, and almost overboard before I caught him.  So dazed were we by the onslaught that the thing—­whatever it was—­could have escaped, and left us none the wiser.  But, although it eluded us in the darkness, it did not leave.  It was there, whimpering to itself, searching for something—­the sheet.  As I steadied Mac, it passed me.  I caught at it.  Immediately the struggle began all over again.  But this time we had the advantage, and kept it.  After a battle that seemed to last all night, and that was actually fought all over that part of the deck, we held the creature subdued, and Mac, getting a hand free, struck a match.