“Yes, it is this: the fact that the poisoning occurred—as it appears—only when Mrs. Monkhouse was away from home, suggests not only that the poisoner was fully cognizant of her movements, which all the household would be, but that her presence at home would have hindered that poisoner from administering the poison. Now, the different persons in the house would be differently affected by her presence. We need not pursue the matter any further just now, but you must see that the hindrance to the poisoning caused by Mrs. Monkhouse’s presence would be determined by the nature of the relations between Mrs. Monkhouse and the poisoner.”
“Yes, I see that.”
“And you see that this circumstance tends to confirm the belief that the crime was committed by a member of the household?”
“I suppose it does,” I admitted, grudgingly.
“It does, certainly,” said Thorndyke; “and that being so, I ask you again: do you think it expedient that you should meddle with this case? If you do, you will be taking a heavy responsibility; for I must remind you that you are not proposing to employ me as a counsel, but as an investigator who may become a witness. Now, when I plead in court, I act like any other counsel; I plead my client’s case frankly as an advocate, knowing that the judge is there to watch over the interests of justice. But as an investigator or witness I am concerned only with the truth. I never give ex parte evidence. If I investigate a crime and discover the criminal, I denounce him, even though he is my employer; for otherwise I should become an accessory. Whoever employs me as an investigator of crime does so at his own risk.
“Bear this in mind, Mayfield, before you go any further in this matter. I don’t know what your relations are to these people, but I gather that they are your friends; and I want you to consider very seriously whether you are prepared to risk the possible consequences of employing me. It is actually possible that one or more of these persons may be indicted for the murder of Harold Monkhouse. That would, in any case, be extremely painful for you. But if it happened through the action of the police, you would be, after all, but a passive spectator of the catastrophe. Very different would be the position if it were your own hand that had let the axe fall. Are you prepared to face the risk of such a possibility?”
I must confess that I was daunted by Thorndyke’s blunt statement of the position. There was no doubt as to the view that he took of the case. He made no secret of it. And he clearly gauged my own state of mind correctly. He saw that it was not the crime that was concerning me; that I was not seeking justice against the murderer but that I was looking to secure the safety of my friends.
I turned the question over rapidly in my mind. The contingency that Thorndyke had suggested was horrible. I could not face such a risk. Rather, by far, would I have had the murderer remain unpunished than be, myself, the agent of vengeance on any of these suspects. Hideous as the crime was, I could not bring myself to accept the office of executioner if one of my own friends was to be the victim.
I had almost decided to abandon the project and leave the result to Fate or the police. But then came a sudden revulsion. From the grounds of suspicion my thoughts flew to the persons suspected; to gentle, sympathetic Madeline, so mindful of the dead man’s comfort, so solicitous about his needs, so eager to render him the little services that mean so much to a sick man. Could I conceive of her as hiding under this appearance of tender sympathy the purposes of a cruel and callous murderess? The thing was absurd. My heart rejected it utterly. Nor could I entertain for a moment such a thought of the kindly, attentive housemaid; and even Wallingford, much as I disliked him, was obviously outside the area of possible suspicion. An intolerable coxcomb he certainly was; but a murderer—never!
“I will take the risk, Thorndyke,” said I.