"I'll take a little walk in the park," said the sarcastic Mr. Ela. T. B. went back to his room, Ela following. He switched on the light, but stood still in the doorway. In the ten minutes' absence some one had been there. Two drawers of the desk had been forced; the floor was littered with papers flung there hurriedly by the searcher. T. B. stepped swiftly to the desk--the envelope had gone. A window was open and the fog was swirling into the room. "There's blood here," said Mr. Ela. He pointed to the dappled blotting pad. "Cut his hand on the glass," said T. B. and jerked his head to the broken pane in the window. He peered out through the open casement. A hook ladder, such as American firemen use, was hanging to the parapet. So thick was the fog that it was impossible to see how long the ladder was, but the two men pulled it up with scarcely an effort. It was made of a stout light wood, with short steel brackets affixed at intervals. "Blood on this too," said Ela, then, to the constable who had come to his ring, he jerked his orders rapidly: "Inspector on duty to surround the office with all the reserve--'phone Cannon Row all men available to circle Scotland Yard, and to take into custody a man with a cut hand--'phone all stations to that effect." "There's little chance of getting our friend," said T. B. He took up a magnifying glass and examined the stains on the pad. "Who was he?" asked Ela. T. B. pointed to the stain. "Montague," he said, briefly, "and he now knows the very thing I did not wish him to know." "And that is?" T. B. did not speak for a moment. He stood looking down at the evidence which the intruder had left behind. "He knows how much I know," he said, grimly, "but he may also imagine I know more--there are going to be developments." CHAPTER IV It was a bad night in London, not wild or turbulent, but swathed to the eyes like an Eastern woman in a soft grey garment of fog. It engulfed the walled canyons of the city, through which the traffic had roared all day, plugged up the maze of dark side-streets, and blotted out the open squares. Close to the ground it was thick, viscous, impenetrable, so that one could not see a yard ahead, and walked ghostlike, adventuring into a strange world. Occasionally it dispersed. In front of the Jollity Theatre numbers of arc-lights wrought a wavering mist-hung yellow space, into which a constant line of vehicles, like monstrous shiny beetles, emerged from the outer nowhere, disgorged their contents, and were eclipsed again. And pedestrians in gay processional streamed across the rudy glistening patch like figures on a slide. Conspicuous in the shifting throng was a sharp-faced boy, ostensibly selling newspapers, but with a keen eye upon the arriving vehicles. Suddenly he darted to the curb, where an electric coupe had just drawn up. A man alighted heavily, and turned to assist a young woman.