A cry from beyond the bolted door-a thick, desperate croaking that gaspingly repeated a name. Stuart Brent paused in the act of filling a whisky glass, and shot a startled glance toward the door from beyond which that cry had come. It was his name that had been gasped out-and why should anyone call on him with such frantic urgency at midnight in the hall outside his apartment?He stepped to the door, without stopping to set down the square amber bottle. Even as he turned the knob, he was electrified by the unmistakable sounds of a struggle outside-the quick fierce scuff of feet, the thud of blows, then the desperate voice lifted again. He threw the door open.The richly appointed hallway outside was dimly lighted by bulbs concealed in the jaws of gilt dragons writhing across the ceiling. The costly red rugs and velvet tapestries seemed to drink in this soft light, heightening an effect of unreality. But the struggle going on before his eyes was as real as life and death.There were splashes of a brighter crimson on the dark-red rug. A man was down on his back before the door, a slender man whose white face shone like a wax mask in the dim light. Another man crouched upon him, one knee grinding brutally into his breast, one hand twisting at the victim's throat. The other hand lifted a red-smeared blade.Brent acted entirely through impulse. Everything happened simultaneously. The knife was swinging up for the downward drive even as he opened the door. At the height of its arc it hovered briefly as the wielder shot a venomous, slit-eyed glance at the man in the doorway. In that instant Brent saw murder about to be done, saw that the victim was a white man, the killer a swarthy alien of some kind. Age-old implanted instincts acted through him, without his conscious volition. He dashed the heavy whisky bottle full into the dark face with all his power. The hard, stocky body toppled backward in a crash of broken glass and a shower of splattering liquor, and the knife rang on the floor several feet away. With a feline snarl the fellow bounced to his feet, red-eyed, blood and whisky streaming from his face and over his collar.For an instant he crouched as if to leap at Brent barehanded. Then the glare in his eyes wavered, turned to something like fear, and he wheeled and was gone, lunging down the stair with reckless haste. Brent stared after him in amazement. The whole affair was fantastic, and Brent was irritated. He had broken a self-imposed rule of long standing-which was never to butt into anything which was not his business."Brent!" It was the wounded man, calling him weakly.Brent bent down to him."What is it, old fellow-Thunderation! Stockton!""Get me in, quick!" panted the other, staring fearfully at the stair. "He may come back-with others."Brent stooped and lifted him bodily. Stockton was not a bulky man, and Brent's trim frame concealed the muscles of an athlete. There was no sound throughout the building. Evidently no one had been aroused by the muffled sounds of the brief fight. Brent carried the wounded man into the room and laid him carefully on a divan. There was blood on Brent's hands when he straightened."Lock the door!" gasped Stockton.