It was four o'clock when he arrived in the neighbourhood of Soho. The sky was growing darker every minute; but there was still light sufficient to distinguish the passers-by. At the entrance to Poplar Street he was passed by a man walking swiftly--a tall, fair-bearded man, who looked neither to right nor left, but raced on breathlessly towards No. 49. Instinctively Mallow guessed this was his enemy. "Francis Hain, to a certainty," he muttered under his breath; "light hair, light beard, tall, thin--the exact description given in the papers. Will he enter No. 49?" At No. 49, surely enough, the man pulled up, and admitting himself, evidently with a latch-key, disappeared within. Mallow's hot blood was at boiling point. Here was the wretch who had murdered the unfortunate Carson within his grasp. Heedless of the danger he was running, he knocked at the door of No. 49. It was opened almost immediately. He had given the signal knock which Rouge had taught him. The door-keeper recognized him at once, and the next minute he was standing in the dark passage of that dangerous den. "Where is the gentleman who entered just now?" he asked the door-keeper breathlessly. "Upstairs; he goes to see Madame," replied the man, who had no idea that anything was wrong. Mallow had given the signal, and his face was known to him. The door-keeper was quite easy in his mind. Up the narrow stairs Mallow sprang two at a time, reckless, and full of fierce courage. He was determined to face Hain, and wring the truth from him at all costs. Caution, wisdom, fear, all went to the four winds. The hot Irish fighting blood fizzled through his veins--burned in his cheek. Rash and unthinking, he dashed forward with a courage absolutely blind--the courage which wins or loses all. On the first landing he caught a glimpse of a tall figure. He heard the click of a turning door-knob. The next moment Mallow the hero, Mallow the fool, had flung open the door and stood on the threshold of Mrs. Arne's room. She was there, and near her stood the man Hain. "At last!" cried Mallow between his teeth. "At last I have got you." "What does he mean?" demanded Madame, in her metallic voice. "It means that I want Francis Hain for murder." The tall man slipped back a pace. His voice quavered. "I am not Hain," he said, keeping a wary eye on Mallow. "You liar!" Mallow sprang forward. "You are Hain the murderer. You and that woman--one of you--killed young Carson." "Madman! Carson is alive in Italy." "Carson is dead--murdered! You killed him. You are Hain." "He is not Hain," said Mrs. Arne, simply. "I am not Hain," repeated the man. Something in the tone of his voice sounded strangely familiar to Mallow. "No, you are not Hain," said Mallow, throwing himself at the man's throat. "I know you now--you are Drabble"--his hand twitched away the light beard, and the doctor's clean-shaven face was revealed--"Drabble the murderer!" "Kill the spy," breathed Madame Death-in-Life; "he knows too much."