“Rot!” ejaculated the other impatiently.  “What are you talking about?”

“Now, listen to me, Greene,” said Marriott, as calmly as he could, for the breathing was still plainly audible, “and I’ll tell you what I mean, only don’t interrupt.”  And thereupon he related exactly what had happened during the night, telling everything, even down to the pain in his arm.  When it was over he got up from the table and crossed the room.

“You hear the breathing now plainly, don’t you?” he said.  Greene said he did.  “Well, come with me, and we’ll search the room together.”  The other, however, did not move from his chair.

“I’ve been in already,” he said sheepishly; “I heard the sounds and thought it was you.  The door was ajar—­so I went in.”

Marriott made no comment, but pushed the door open as wide as it would go.  As it opened, the sound of breathing grew more and more distinct.

“Someone must be in there,” said Greene under his breath.

“Someone is in there, but where?” said Marriott.  Again he urged his friend to go in with him.  But Greene refused point-blank; said he had been in once and had searched the room and there was nothing there.  He would not go in again for a good deal.

They shut the door and retired into the other room to talk it all over with many pipes.  Greene questioned his friend very closely, but without illuminating result, since questions cannot alter facts.

“The only thing that ought to have a proper, a logical, explanation is the pain in my arm,” said Marriott, rubbing that member with an attempt at a smile.  “It hurts so infernally and aches all the way up.  I can’t remember bruising it, though.”

“Let me examine it for you,” said Greene.  “I’m awfully good at bones in spite of the examiners’ opinion to the contrary.”  It was a relief to play the fool a bit, and Marriott took his coat off and rolled up his sleeve.

“By George, though, I’m bleeding!” he exclaimed.  “Look here!  What on earth’s this?”

On the forearm, quite close to the wrist, was a thin red line.  There was a tiny drop of apparently fresh blood on it.  Greene came over and looked closely at it for some minutes.  Then he sat back in his chair, looking curiously at his friend’s face.

“You’ve scratched yourself without knowing it,” he said presently.

“There’s no sign of a bruise.  It must be something else that made the arm ache.”

Marriott sat very still, staring silently at his arm as though the solution of the whole mystery lay there actually written upon the skin.

“What’s the matter?  I see nothing very strange about a scratch,” said Greene, in an unconvincing sort of voice.  “It was your cuff links probably.  Last night in your excitement—­”

But Marriott, white to the very lips, was trying to speak.  The sweat stood in great beads on his forehead.  At last he leaned forward close to his friend’s face.