O'Brien bared his leg: the injury was now nearly healed; but was still enough to make the man limp. Then, as he bent down to readjust his trousers Oakes, accidentally as it were, brushed against his forehead, throwing back the hair from O'Brien's brow. We all saw a long, white, glistening scar, now exposed to full view at the line of the heavy hair. The man before us _was_ Larkin the detective. Oakes with marvelous tranquillity apologized for the "accident," and said: "Why should Maloney have shot you? what is behind it all? Speak." "I do not know." It was evident to us all that O'Brien was avoiding the issue. "I see," exclaimed Oakes. "As O'Brien you know nothing; as Mr. Larkin the detective you know more than it suits you to tell." O'Brien was on his feet in an instant. "Who dares insinuate--who dares say I am a detective, sir?" "Nonsense! Keep cool. The Chief here has satisfied himself. Tell us--why should Maloney hate you?" O'Brien glanced around and fixed his gaze on Hallen. "I am Larkin. He hates me because I have been watching him. Maloney is the man responsible for the Mansion mysteries, I think," he said. "Indeed! What else?" queried Hallen suddenly. "I believe he may be the murderer of Mr. Mark." "What proofs have you?" asked Oakes, as we all leaned forward intently. "No proof as yet." "Exactly! But, Mr. Larkin, you deserve much credit," said Oakes, as he led O'Brien to a chair by Hallen's side. "Sit here," he continued. "I am going to have Maloney brought in now. He has always been a good gardener--a decent sort of fellow. I must hear his story before I give him up to the Chief. It has been suggested that Maloney may be mentally unbalanced; you will excuse me, Mr. Larkin, if I use you as a foil to draw him out while Dr. Moore assists me." Then, by way of explanation, Oakes, whose identity was still unknown to Larkin, went on: "You see, Chief Hallen wishes to be sure of some little points, and so do I. Perhaps Maloney will not resent my questioning; he should have no feelings against the agent of this property, whereas he might object to Hallen as an interlocutor." Oakes was now a trifle pale, I thought. There were furrows on his forehead; his manner was suave and deliberately slow. But little did I dream the true depth of the man, the masterly manner in which he was about to test the mental balance of Maloney. To one who was ignorant of the terrible events this story tells of, and the dire necessity of discovering once for all who was responsible for them, the efforts of these keen, scientific men to entrap a weakened brain would have seemed unfair and cruel. But for those who knew the story and knew of the murderous deeds done in Mona by some unfortunate with a cunning, diabolic, although probably unbalanced mind, there remained only one alternative--to uncover and catch the criminal at all hazards.