No sooner had the shuffle of her footsteps died away than Kennedy was on his feet, listening intently at the door.  There was no sound.  He took a chair and tiptoed out into the dark hall with it.  Turning it upside down he placed it at the foot of the stairs with the four legs pointing obliquely up.  Then he drew me into a corner with him.

How long we waited I cannot say.  The next I knew was a muffled step on the landing above, then the tread on the stairs.

A crash and a deep volley of oaths in French followed as the man pitched headlong over the chair on the dark steps.

Kennedy whipped out his revolver and fired pointblank at the prostrate figure.  I do not know what the ethics are of firing on a man when he is down, nor did I have time to stop to think.

Craig grasped my arm and pulled me toward the door.  A sickening odour seemed to pervade the air.  Upstairs there was shouting and banging of doors.

“Closer, Walter,” he muttered, “closer to the door, and open it a little, or we shall both be suffocated.  It was the Secret Service gun I shot off—­the pistol that shoots stupefying gas from its vapour-filled cartridges and enables you to put a criminal out of commission without killing him.  A pull of the trigger, the cap explodes, the gunpowder and the force of the explosion unite some capsicum and lycopodium, producing the blinding, suffocating vapour whose terrible effect you see.  Here, you upstairs,” he shouted, “advance an inch or so much as show your heads over the rail and I pump a shot at you, too.  Walter, take the gun yourself.  Fire at a move from them.  I think the gases have cleared away enough now.  I must get him before he recovers consciousness.”

A tap at the door came, and without taking my eyes off the stairs I opened it.  Burke slid in and gulped at the nauseous atmosphere.

“What’s up?” he gasped.  “I heard a shot.  Where’s Kennedy?”

I motioned in the darkness.  Kennedy’s electric bull’s-eye flashed up at that instant and we saw him deftly slip a bright pair of manacles on the wrists of the man on the floor, who was breathing heavily, while blood flowed from a few slight cuts due to his fall.

Dexterously as a pickpocket Craig reached into the man’s coat, pulled out a packet of papers, and gazed eagerly at one after another.  From among them he unfolded one written in French to Madame Marie de Nevers some weeks before.  I translate: 

Dear Marie:  Herr Schmidt informs me that his agent in the War Department at Washington, U. S. A., has secured some important information which will interest the Government for which Herr Schmidt is the agent—­of course you know who that is.

It is necessary that you should carry the packet which will be handed to you (if you agree to my proposal) to New York by the steamer Tripolitania.  Go to the Vandeveer Hotel and in a few days, as soon as a certain exchange can be made, either our friend in Washington or myself will call on you, using the name Gonzales.  In return for the package which you carry he will hand you another.  Lose no time in bringing the second package back to Paris.