“It is possible,” he said, half to himself, “to identify a person by means of the arrangement of the sweat glands or pores.  Poroscopy, Dr. Edmond Locard, director of the Police Laboratory at Lyons, calls it.  The shape, arrangement, number per square centimeter, all vary in different individuals.  Besides, here we have added the lines of the forehead.”

He was studying the two impressions intensely.  When he looked up from his examination, his face wore a peculiar expression.

“This is not the head which was placed so close to the glass of the door of Schloss’ office, peering through, on the night of the robbery, in order to see before picking the lock whether the office was empty and everything ready for the hasty attack on the safe.”

“That disposes of my theory that Schloss robbed himself,” remarked Winters reluctantly.  “But the struggle here, the sleeve of the dress, the pistol—­could he have been shot?”

“No, I think not,” considered Kennedy.  “It looks to me more like a case of apoplexy.”

“What shall we do?” asked Winters.  “Far from clearing anything up, this complicates it.”

“Where’s Muller?” asked Kennedy.  “Does he know?  Perhaps he can shed some light on it.”

The clang of an ambulance bell outside told that the aid summoned by Winters had arrived.

We left the body in charge of the surgeon and of a policeman who arrived about the same time, and followed Winters.

Muller lived in a cheap boarding house in a shabbily respectable street downtown, and without announcing ourselves we climbed the stairs to his room.  He looked up surprised but not disconcerted as we entered.

“What’s the matter?” he asked.

“Muller,” shot out Winters, “we have just found Mr. Schloss dead!”

“D-dead!” he stammered.

The man seemed speechless with horror.

“Yes, and with his grips packed as if to run away.”

Muller looked dazedly from one of us to the other, but shut up like a clam.

“I think you had better come along with us as a material witness,” burst out Winters roughly.

Kennedy said nothing, leaving that sort of third degree work to the detective.  But he was not idle, as Winters tried to extract more than the monosyllables, “I don’t know,” in answer to every inquiry of Muller about his employer’s life and business.

A low exclamation from Craig attracted my attention from Winters.  In a corner he had discovered a small box and had opened it.  Inside was a dry battery and a most peculiar instrument, something like a little flat telephone transmitter yet attached by wires to earpieces that fitted over the head after the manner of those of a wireless detector.

“What’s this?” asked Kennedy, dangling it before Muller.

He looked at it phlegmatically.  “A deaf instrument I have been working on,” replied the jeweler.  “My hearing is getting poor.”