Her shriek of terror had scarcely escaped when the detective, coolly stepping forward from his watch, dealt the ruffian a blow on the back of the head with his horny fist, which felled him like an ox, and the leveled pistol fell from his relaxing hand and snapped off with the concussion, lodging its bullet in the bottom panel of the nearest railway car and startling the cabman's horses so violently that they plunged off the platform with the cabman clinging to the reins. A railway porter ran up to the scene of the assault, and held the half-stunned O'Grady while the detective secured him, and Purcell, having gathered himself up, with aching bones, led the agitated Margaret into the station-house. By this time the mob had assembled, and were crushing each other unceremoniously to gain a glimpse of the prisoner, who lay cursing and blaspheming on the wooden floor, with his conquerer grimly standing over him, until Adams rattled up in the cab he had been in search of and shared the onerous duty of jailer. Margaret, glancing shudderingly out of the station-house window, saw the wretched man pass on his way to the police station, his captors on either side urging him to hasten. His hands were tied behind him, his florid face was yellow with despair, his steel-blue eyes glared with fear; a more abject picture of crime and ruin could scarce be conceived. And when this wretched vision had vanished, another took its place. A writhing, white face flitted, specter-like, from out of dim shadows, and peered with staring eyeballs after the arrested man, and a scowl of fury, terror, and despair descended on that devilish brow. The next instant he, too, had melted into shadow, and was lost amid the throng. "Roland Mortlake," whispered Margaret, who was shivering as if she had seen a phantom. "He has learned the truth. Great Heaven! he will escape." She stepped to the door and called the steward, who had gone to open the cab-door. "Go instantly in search of Mortlake," she cried; "he has just passed the window; you must not permit him to escape. I will drive to Emersham's law-office myself." Away ran Purcell after two constables; and Margaret hurried into the cab, and, undeterred by one heart-beat of compunction, she set herself to compass her enemy's utter ruin. For pitiful, kind, and great-hearted as she was, she could never suffer a murderer to escape. No, not even to buy her own safety. Margaret Walsingham alighted from the carriage at the door of Mr. Emersham's law-office, and stepped into the room with the mien of a Semiramis, flashing-eyed, carmine cheeked, and inexorable. One glance around the room showed her the nimble young lawyer, and the trembling old clergyman gazing white lipped into each other's faces, the folded paper on the table between them, the locked pocket-book, and the will; and the hand of the clock on the mantle-piece pointed to the fifteenth minute after seven. "Thank God! she is here," murmured Mr. Challoner, solemnly.