The man moved off, and the door was opened.  Smith whispered in my ear: 

“Some creature of Dr. Fu-Manchu is in the hotel!”

Mr. Graham Guthrie, British resident in North Bhutan, was a big, thick-set man—­gray-haired and florid, with widely opened eyes of the true fighting blue, a bristling mustache and prominent shaggy brows.  Nayland Smith introduced himself tersely, proffering his card and an open letter.

“Those are my credentials, Mr. Guthrie,” he said; “so no doubt you will realize that the business which brings me and my friend, Dr. Petrie, here at such an hour is of the first importance.”

He switched off the light.

“There is no time for ceremony,” he explained.  “It is now twenty-five minutes past twelve.  At half-past an attempt will be made upon your life!”

“Mr. Smith,” said the other, who, arrayed in his pajamas, was seated on the edge of the bed, “you alarm me very greatly.  I may mention that I was advised of your presence in England this morning.”

“Do you know anything respecting the person called Fu-Manchu—­Dr. Fu-Manchu?”

“Only what I was told to-day—­that he is the agent of an advanced political group.”

“It is opposed to his interests that you should return to Bhutan.  A more gullible agent would be preferable.  Therefore, unless you implicitly obey my instructions, you will never leave England!”

Graham Guthrie breathed quickly.  I was growing more used to the gloom, and I could dimly discern him, his face turned towards Nayland Smith, whilst with his hand he clutched the bed-rail.  Such a visit as ours, I think, must have shaken the nerve of any man.

“But, Mr. Smith,” he said, “surely I am safe enough here!  The place is full of American visitors at present, and I have had to be content with a room right at the top; so that the only danger I apprehend is that of fire.”

“There is another danger,” replied Smith.  “The fact that you are at the top of the building enhances that danger.  Do you recall anything of the mysterious epidemic which broke out in Rangoon in 1908—­the deaths due to the Call of Siva?”

“I read of it in the Indian papers,” said Guthrie uneasily.  “Suicides, were they not?”

“No!” snapped Smith.  “Murders!”

There was a brief silence.

“From what I recall of the cases,” said Guthrie, “that seems impossible.  In several instances the victims threw themselves from the windows of locked rooms—­and the windows were quite inaccessible.”

“Exactly,” replied Smith; and in the dim light his revolver gleamed dully, as he placed it on the small table beside the bed.  “Except that your door is unlocked, the conditions to-night are identical.  Silence, please, I hear a clock striking.”

It was Big Ben.  It struck the half-hour, leaving the stillness complete.  In that room, high above the activity which yet prevailed below, high above the supping crowds in the hotel, high above the starving crowds on the Embankment, a curious chill of isolation swept about me.  Again I realized how, in the very heart of the great metropolis, a man may be as far from aid as in the heart of a desert.  I was glad that I was not alone in that room—­marked with the death-mark of Fu-Manchu; and I am certain that Graham Guthrie welcomed his unexpected company.