Out onto the paved pathway communicating with the wharf came Smith, shepherding his tottering charge.  I was too far away to hear any conversation that might take place between the two, but, unless Smith gave the pre-arranged signal, I must approach no closer.  Thus, as one sees a drama upon the screen, I saw what now occurred—­occurred with dramatic, lightning swiftness.

Releasing Smith’s arm, the old woman suddenly stepped back ... at the instant that another figure, a repellent figure which approached, stooping, apish, with a sort of loping gait, crossed from some spot invisible to me, and sprang like a wild animal upon Smith’s back!

It was a Chinaman, wearing a short loose garment of the smock pattern, and having his head bare, so that I could see his pigtail coiled upon his yellow crown.  That he carried a cord, I perceived in the instant of his spring, and that he had whipped it about Smith’s throat with unerring dexterity was evidenced by the one, short, strangled cry that came from my friend’s lips.

Then Smith was down, prone upon the crazy planking, with the ape-like figure of the Chinaman perched between his shoulders—­bending forward—­ the wicked yellow fingers at work, tightening—­tightening—­tightening the strangling-cord!

Uttering a loud cry of horror, I went racing along the gangway which projected actually over the moving Thames waters, and gained the wharf.  But, swift as I had been, another had been swifter!

A tall figure (despite the brilliant moon, I doubted the evidence of my sight), wearing a tweed overcoat and a soft felt hat with the brim turned down, sprang up, from nowhere as it seemed, swooped upon the horrible figure squatting, simianesque, between Smith’s shoulder-blades, and grasped him by the neck.

I pulled up shortly, one foot set upon the wharf.  The new-comer was the double of Nayland Smith!

Seemingly exerting no effort whatever, he lifted the strangler in that remorseless grasp, so that the Chinaman’s hands, after one quick convulsive upward movement, hung limply beside him like the paws of a rat in the grip of a terrier.

“You damned murderous swine!” I heard in a repressed, savage undertone.  “The knife failed, so now the cord has an innings!  Go after your pal!”

Releasing one hand from the neck of the limp figure, the speaker grasped the Chinaman by his loose, smock-like garment, swung him back, once—­a mighty swing—­and hurled him far out into the river as one might hurl a sack of rubbish!

CHAPTER XXIII

ARREST OF SAMARKAN

“As the high gods willed it,” explained Nayland Smith, tenderly massaging his throat, “Mr. Forsyth, having just left the docks, chanced to pass along Three Colt Street on Wednesday night at exactly the hour that I was expected!  The resemblance between us is rather marked and the coincidence of dress completed the illusion.  That devilish Eurasian woman, Zarmi, who has escaped us again—­of course you recognized her?—­made a very natural mistake.  Mr. Forsyth, however, made no mistake!”