encountered in homes for the moment untenanted.

Down the hall was an open double doorway. Keane stared that way. He himself could not have told how he knew, but know he did, that beyond that doorway lay what he had come to find. He walked toward it.

Behind him, the street door opened again, very slowly and cautiously. An eye was put close to the resultant crack. The eye was dark, exotically lovely. It fastened on Keane's back.

Keane stared in through the doorway. He was gazing into a library, dimmed by drawn shades. He entered it, with every nerve-end in his body silently shrieking of danger.

The street door softly closed after admitting a figure that moved on soundless feet. A woman, with a face like a pale flower on an exquisite throat. Madame Sin.

Her face was as serenely lovely as ever. Not by a line had it changed. And yet, subtly, it had become a mask of beautiful death. Her eyes were death's dark fires as she moved without a sound down the hall toward the library. In her tapering hands was the gold-link bag.

In the library, Keane stood with beating heart over two stark, still bodies that lay on the thick carpet near a flat-topped desk. One was wizened, lank, a little undersized, with dry-looking skin. It was the body of Chichester. At first it seemed a corpse, but then Keane saw the chest move with slow, deep breaths, as the breast of the woman back at the hotel had moved.

But it was not this figure that made Keane's heart thud and his hands clench. It was the other.

This was a taller figure, lying on its back with hands folded. The hands were red-gloved. The face was concealed by a red mask. The body was draped by a red cloak. From the head sprang two little knobs, or projections, like Lucifer's horns. Doctor Satan himself!

"It's my chance," whispered Keane. "Satan—sending his soul and mind and spirit from his own shell—into that of others—Madame Sin—Chichester. Now his body lies here empty! If I killed that——"

Exotically beautiful dark eyes—with death in their loveliness—watched him from the library doorway as he bent over the red-robed figure. Sardonic death in lovely eyes!

"No wonder Gest thought that Wilson was killed in the conference room, just before he could tell of the roulette wheel, as if Doctor Satan had been there himself! Satan was there! And he was on the roof garden earlier, and in the roulette room! A trance for the woman, the crowding of Satan's black spirit into her body—and she becomes Madame Sin, with Satan peering from her eyes and moving in her mantle of flesh! A trance for the unfortunate Chichester—and Satan talks with Gest and Kroner as the Blue Bay treasurer, and can strike down Wilson when he comes to report! Chichester and Madame Sin—both Doctor Satan—becoming lifeless, trance-held shells when Satan's soul has left them!"

But here was Satan's physical shell, lying in a coma at his feet, to be killed at a stroke! His deadly enemy, the enemy of all mankind, delivered helpless to him!

"But if I do kill the body," Keane whispered, "will I kill the spirit too, or banish it from the material world so that humanity won't again be troubled? Satan's spirit, the essential man, is abroad in another body. If I kill this red-robed body, will it draw the spirit out of mortal affairs with it? Or would it simply deprive it of its original housing so that I'd have to seek Satan's soul in body after body, as I have till now sought him in the flesh in lair after lair? That would be—horrible!"

He drove away the grim thought. It was probable that with the death of his body, Doctor Satan in entirety would die, or at least pass out of mortal knowledge through the gateway called death. And the mechanics of forcing him through that gateway was to kill the body.

Behind him, Madame Sin crept closer and closer on soundless feet. Her red lips were set in a still smile. The gold-link purse was extended a little toward Keane. Her forefinger searched for the movable bar that changed angles of the queer, metal cage within.

Keane's hand raised to strike. His eyes burned down at the red-clad figure of the man at his feet, who was mankind's enemy. Behind him, Madame Sin's finger found the little bar....

It was not till then that Keane felt the psychic difference caused by the entrance of another into a room that had been deserted save for himself. Another person would not have felt that difference at all, but Keane had developed his psychic perceptions as ordinary men exercise and develop their biceps.

With an inarticulate cry he whirled, and leaped far to the side.