“Follow that cab!  Don’t let the man in it suspect, but follow, and don’t lose sight of it!”

They were off!

Helen glanced ahead quickly, and was just in time to see Gianapolis’ cab disappear; then, leaning out of the window, she indulged in an extravagant pantomime for the benefit of Denise Ryland, who was hurrying after her.

“Take the next cab and follow me!” she cried, whilst her friend raised her hand to her ear the better to detect the words.  “I cannot wait for you or the track will be lost"...

Helen’s cab swung around the corner—­and she was not by any means certain that Denise Ryland had understood her; but to have delayed would have been fatal, and she must rely upon her friend’s powers of penetration to form a third in this singular procession.

Whilst these thoughts were passing in the pursuer’s mind, Gianapolis, lighting a cigarette, had thrown himself back in a corner of the cab and was mentally reviewing the events of the evening—­that is, those events which were associated with Helen Cumberly.  He was disappointed but hopeful:  at any rate he had suffered no definite repulse.  Without doubt, his reflections had been less roseate had he known that he was followed, not only by two, but by three trackers.

He had suspected for some time now, and the suspicion had made him uneasy, that his movements were being watched.  Police surveillance he did not fear; his arrangements were too complete, he believed, to occasion him any ground for anxiety even though half the Criminal Investigation Department were engaged in dogging his every movement.  He understood police methods very thoroughly, and all his experience told him that this elusive shadow which latterly had joined him unbidden, and of whose presence he was specially conscious whenever his steps led toward Palace Mansions, was no police officer.

He had two theories respecting the shadow—­or, more properly, one theory which was divisible into two parts; and neither part was conducive to peace of mind.  Many years, crowded with many happenings, some of which he would fain forget, had passed since the day when he had entered the service of Mr. King, in Pekin.  The enterprises of Mr. King were always of a secret nature, and he well remembered the fate of a certain Burmese gentleman of Rangoon who had attempted to throw the light of publicity into the dark places of these affairs.

From a confidant of the doomed man, Gianapolias had learned, fully a month before a mysterious end had come to the Burman, how the latter (by profession a money-lender) had complained of being shadowed night and day by someone or something, of whom or of which he could never succeed in obtaining so much as a glimpse.

Gianapolis shuddered.  These were morbid reflections, for, since he had no thought of betraying Mr. King, he had no occasion to apprehend a fate similar to that of the unfortunate money-lender of Rangoon.  It was a very profitable service, that of Mr. King, yet there were times when the fear of his employer struck a chill to his heart; there were times when almost he wished to be done with it all...