“If ever I can show my gratitude for what you have done for me this night,” he said with deep feeling, “believe me I will!” “It’s all in the day’s work,” said Desmond as he accompanied them to the door. “Good-bye.” “_Au revoir!_” corrected Francis smilingly as he followed the Air Marshal out. For full five minutes after they had gone, Desmond remained standing in the hall, sunk in his thoughts. He was interrupted by Sergeant Rushbrooke. “Beg pardon, sir!” said the plain-clothes man, “but I believe there’s some one on the stairs outside!” Like a flash Desmond’s hand shot out at the electric-light switch at the door of the sitting-room. There was a click and the room was plunged in darkness. Desmond pulled out an automatic. “Have your gun ready!” he whispered to the detective. “Keep very quiet, but be prepared to shoot!” The flat was in complete darkness. Before them, as they crouched behind the table, they saw the dim outline of the bedroom door. Beyond, where the kitchen lay, was blackness. Very faintly, from the obscurity before them, a key rattled. Presently the cold night air softly brushed their faces. At the end of the flat against a background of silver moonlight a huge figure bulked immensely. A door closed softly and darkness fell again. A heavy limping sound approached them; a step and a stump, a step and a stump, muted but audible. They could hear the floor boards straining as beneath some immense weight. And now that uncouth shape loomed gigantic in the doorway of the sitting-room. Its breadth seemed to stretch from jamb to jamb. Some movement must have betrayed their presence, for there came the rasp of a harsh ejaculation. Then the room was flooded with light and Desmond’s voice rang out: “If you move I’ll shoot!” It was Grundt, bareheaded, in the clothes of rusty black he always affected, his right hand, plumed with black hair on the back, grasping his rubber-shod crutch-stick. He had made a half-turn in the doorway, and now twisted his head round to stare at his challenger, his burning eyes blazing defiance, his cruel, fleshy lips pursed up in a contemptuous sneer. “You can put your hands up, Herr Doktor!” said Desmond. “Quickly, please, or there might be an accident! And you can drop your stick!” The giant cripple faced his aggressors squarely. He hesitated for an instant, then, with an almost imperceptible shrug of his shoulders, he slowly raised his hands, his stick rattling to the floor. “Sergeant, would you mind . . .?” Desmond remarked in a colloquial tone. Sergeant Rushbrooke crossed to the doorway and, with a dexterity born of long experience, ran his fingers lightly over the big man’s pockets, not forgetting, you may be sure, the inside breast pocket, where your professional gunman mostly carries his weapon, or the armholes of the waistcoat, very handy for concealing a knife. “He’s not armed, sir,” he reported.