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 hi