These instructions fulfilled, the spinster sought the retirement of her room, surrendered herself to the enjoyment of reminiscent digestion, and Raikes began to pull himself together.

His method was characteristic.

On the basis that he could not afford to enjoy himself like any normally constituted being, he assured his mind that he could not submit to the expense of illness.

According to his rigid logic, sickness was more the result of indulgence than self-denial.

He proposed to have the credit of his abnegations.

Therefore he directed his perverse will to the contemplation of the rational aspect of his condition, and presently had managed to convince himself that if he did not entertain the belief of suffering, this untoward condition would cease to exist.

As this singular being combatted all that was unwelcome to this point of view, the grim lines tightened about the corners of his mouth, the deep fissures in his forehead established a communication with the obstinate wrinkles at the root of his nose, and by noon he was well on his way to the mastery of his indisposition, and by nightfall he scandalized the young medical attendant by standing up to receive him.

Extending to himself a chuckling tribute of his resolution, he received the incredulity of his nephew as additional indorsement when the latter made his appearance that evening, accompanied by the colorless negation of a man whom he could scarcely persuade himself to believe was the celebrated Gratz.

However, no more ideal countenance could have been created for the purposes to which it was applied by its owner.

Pallid, expressionless, vacant, it was as nearly a canvas upon which to delineate almost anything in the range of emotion as it was possible for a visage of flesh and blood to be.

As to the details of features, these were altogether subordinate, and as devoid of physiognomical meaning as the dull integument which encompassed them.

It had about the same amount of character as a bald baby.

One received the impression that a seismic disturbance might awaken some show of emotion, but design--never.

And yet, behind that pale disguise, between sleepy, level lids, two points of concentrated fire and ceaseless animation gleamed their startling significance to any one able to comprehend.

In stature he was adjusted to his visage.

His frame was lean enough to repudiate the incredible agility and recuperative strength it housed, and his carriage was consistently "out of plumb."

Altogether it was an identity that would have been overlooked in any gathering, and was almost nondescript enough to establish an eligibility to the most exclusive function.

This unpromising ensemble, however, was not misleading to Raikes, who had looked up quickly at the first appearance of the detective, and had seen the sharp, penetrating glance with which Gratz had for an instant surveyed the apartment.

Moreover, the very leanness of the famous official appealed to him.

Here, at least, were none of the obnoxious evidences of repletion which he viewed with such disapprobation in his sturdier nephew.

The man's attire, too, commended him to the starved graces of his spare host. It was as characterless as it was possible for fabric to be, and considered with his meager physique and vacant physiognomy, was a fitting complement to both; an adjustment of component detail too consistent to have been the needless aspect it was designed to present.

With a voice in which the character had been trained away as surely as the charity from the opinions of the social elite, this descendant of Lecocq accosted his patron, and with business-like brevity indicated that he was already familiar with the situation as outlined by Robert, and if Mr. Raikes would consent to reply to a few questions it would facilitate matters.

His hearer indicated that he was entirely at the disposal of the detective.

With characteristic concentration, therefore, Gratz began:

"Do you suspect anybody in particular?"

"No."

"That is singular," commented Gratz. "May I ask why? Under such circumstances the mind generally proceeds in some unhappy direction."

"Not in this instance," returned Raikes. "Before I suspect any one, I must assign to him supernatural powers, almost. I will have to explain how it is possible for any one to enter this room, penetrate that recess, make the substitution, and retire, leaving the door in the same condition, precisely as left by me the night before."

"That is the point," replied Gratz. Then, after a moment's reflection, he inquired: "Am I at liberty to nose around this room?"

"Help yourself," answered Raikes.

With this assent, Gratz hurried to the window, examined the sash, considered the sheer depths immediately below, its lack of vicinity to other windows, and last, the strong fastenings, to disturb which would involve a degree of rasp and wrench sufficient to disturb the slumbers of a Rip Van Winkle.

With a countenance as impassive as ever, he returned to Raikes and said:

"Now for the hiding place."

With a grimace of reluctant acquiescence, Raikes, closely regarded by the detective, proceeded to the button in the concave, which he moved with slow manipulation for the edification of the alert watcher, who witnessed, without comment, the displacement of the register and the subsequent revelation of the inner compartment.

"Remove the bags."

At the conclusion of this labor, this impenetrable being produced a small rod of steel from one of his pockets, one end of which concluded in a round knob.

With this he proceeded to rap the walls of the inner recess, a proceeding of which Raikes inquired the purpose.

"I want to ascertain," replied Gratz, "if there is any vacancy on the other side."

"I could have saved you all that trouble," replied Raikes. "This is a false radiator, the real flue is on the other side of the room.

"The rear of this small safe backs up against nearly two feet of solid brickwork.

"Exactly behind that is a room occupied by one no more burglarious than a dressmaker's apprentice."

"Thank you," replied Gratz. "Your information is helpful, but I am never satisfied to rely upon description when investigation is possible.

"Whatever deductions I make from this examination I do not want disturbed, so all the doubts they dissipate are not likely to intrude upon my calculations again."

After a few further taps, in which Raikes could see no better purpose than to retire from an embarrassing position with some show of satisfied motive, Gratz directed that the bags be returned.

For the next few minutes he busied himself with the locks, upon which he experimented with the extraordinary keys which Raikes had given him. He shot the bolts backward and forward; noted the stout bar and the precautions for keeping it in place, and then resumed the seat near the table.

After a few moments he said:

"Tell me what has occurred to you between sunrise and sunset during the last three days."

Raikes recounted his usual round of petty detail, which had no possible bearing upon the problem.

When he had concluded this meager resume, Gratz continued:

"Now tell me about the nights."