The car slowed down in that little bay which contains the entrance to the hotel, and Harley stared fixedly out of the rear window, observing the occupants of all other cars and cabs which were following.  For three minutes or more he remained there watching.  “Go on,” he directed.

Again they proceeded westward and, half-way along Piccadilly, “Stop at the Ritz,” came the order.

The car pulled up before the colonnade and Harley, stepping out, dismissed the man and entered the hotel, walked through to the side entrance, and directed a porter to get him a taxicab.  In this he proceeded to the house of Sir Charles Abingdon.  He had been seeking to learn whether he was followed, but in none of the faces he had scrutinized had he detected any interest in himself, so that his idea that whoever was watching Sir Charles in all probability would have transferred attention to himself remained no more than an idea.  For all he had gained by his tactics, Sir Charles’s theory might be no more than a delusion after all.

The house of Sir Charles Abingdon was one of those small, discreet establishments, the very neatness of whose appointments inspires respect for the occupant.  If anything had occurred during the journey to suggest to Harley that Sir Charles was indeed under observation by a hidden enemy, the suave British security and prosperity of his residence must have destroyed the impression.

As the cab was driven away around the corner, Harley paused for a moment, glancing about him to right and left and up at the neatly curtained windows.  In the interval which had elapsed since Sir Charles’s departure from his office, he had had leisure to survey the outstanding features of the story, and, discounting in his absence the pathetic sincerity of the narrator, he had formed the opinion that there was nothing in the account which was not susceptible of an ordinary prosaic explanation.

Sir Charles’s hesitancy in regard to two of the questions asked had contained a hint that they might involve intimate personal matters, and Harley was prepared to learn that the source of the distinguished surgeon’s dread lay in some unrevealed episode of the past.  Beyond the fact that Sir Charles was a widower, he knew little or nothing of his private life; and he was far too experienced an investigator to formulate theories until all the facts were in his possession.  Therefore it was with keen interest that he looked forward to the interview.

Familiarity with crime, in its many complexions, East and West, had developed in Paul Harley a sort of sixth sense.  It was an evasive, fickle thing, but was nevertheless the attribute which had made him an investigator of genius.  Often enough it failed him entirely.  It had failed him to-night—­or else no one had followed him from Chancery Lane.

It had failed him earlier in the evening when, secretly, he had watched from the office window Sir Charles’s car proceeding toward the Strand.  That odd, sudden chill, as of an abrupt lowering of the temperature, which often advised him of the nearness of malignant activity, had not been experienced.