"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. [Illustration: "The wall behind the spot where he had been disappeared."] The wall behind the spot where he had been disappeared as the gold-link bag continued to point that way. The woman, snarling like a tigress, swung her bag toward Keane in his new position. But Keane was not waiting. He sprang for her. His hand got her wrist and wrenched to get the gold-link purse away from her. It turned toward her, back again toward him, with the little bar moving as her hand was constricted over the thing in the purse.