Mr. Norris West, whose lean, stoic face had latterly figured so often in the daily press, lay upon the floor in the little entrance hall of his chambers, flat upon his back, with the telephone receiver in his hand.

The outer door had been forced by the police.  They had had to remove a piece of the paneling to get at the bolt.  A medical man was leaning over the recumbent figure in the striped pajama suit, and Detective-Inspector Weymouth stood watching him as Smith and I entered.

“He has been heavily drugged,” said the Doctor, sniffing at
West’s lips, “but I cannot say what drug has been used. 
It isn’t chloroform or anything of that nature. 
He can safely be left to sleep it off, I think.”

I agreed, after a brief examination.

“It’s most extraordinary,” said Weymouth.  “He rang up the Yard about an hour ago and said his chambers had been invaded by Chinamen.  Then the man at the ’phone plainly heard him fall.  When we got here his front door was bolted, as you’ve seen, and the windows are three floors up.  Nothing is disturbed.”

“The plans of the aero-torpedo?” rapped Smith.

“I take it they are in the safe in his bedroom,” replied the detective, “and that is locked all right.  I think he must have taken an overdose of something and had illusions.  But in case there was anything in what he mumbled (you could hardly understand him) I thought it as well to send for you.”

“Quite right,” said Smith rapidly.  His eyes shone like steel.  “Lay him on the bed, Inspector.”

It was done, and my friend walked into the bedroom.

Save that the bed was disordered, showing that West had been sleeping in it, there were no evidences of the extraordinary invasion mentioned by the drugged man.  It was a small room—­ the chambers were of that kind which are let furnished—­and very neat.  A safe with a combination lock stood in a corner.  The window was open about a foot at the top.  Smith tried the safe and found it fast.  He stood for a moment clicking his teeth together, by which I knew him to be perplexed.  He walked over to the window and threw it up.  We both looked out.

“You see,” came Weymouth’s voice, “it is altogether too far from the court below for our cunning Chinese friends to have fixed a ladder with one of their bamboo rod arrangements.  And, even if they could get up there, it’s too far down from the roof—­two more stories—­ for them to have fixed it from there.”

Smith nodded thoughtfully, at the same time trying the strength of an iron bar which ran from side to side of the window-sill.  Suddenly he stooped, with a sharp exclamation.  Bending over his shoulder I saw what it was that had attracted his attention.

Clearly imprinted upon the dust-coated gray stone of the sill was a confused series of marks—­tracks call them what you will.

Smith straightened himself and turned a wondering look upon me.