"First, your friend Mr. Cleugh must not go near the park. I've already written him a note to that effect. Secondly, you must act exactly as I direct. A single slip will mean that the individual will escape, and in this we must not court failure by any indiscreet move." "And how do you intend that I should act?" I asked, sitting back in my writing-chair and looking at the shrewd detective who was known throughout London as one of the cleverest unravellers of crime, and who had been successful in so many cases wherein human life had been involved. "Well," he said, hesitating, "truth to tell, I would rather that you didn't go to the park at all." "Why?" "Because you could not wait about in the vicinity of the spot indicated without betraying a sign that you were in expectation of some one," he answered. "Remember, you are not a detective." "No," I answered, "I'm not a detective, but I've had a few years' training in investigations. I think I could disguise my anxiety sufficiently." I was extremely anxious to keep the appointment, and his suggestion that I should not go caused me disappointment and annoyance. "But if you were seen waiting about, the man we want would certainly not make his appearance. He'd scent danger at once. We've evidently got to deal with a very cunning scoundrel." "I could conceal myself," I declared. "I promise you I will act with greatest discretion." "Well," he said at length, after some further demur, "I suppose, then, you must have your own way. Personally, I don't think the man will be such a fool as to run his neck into a noose. There's been some clever work in connexion with this matter, and men capable of such ingenuity must be veritable artists in crime and not given to the committal of any indiscretion. The voice in the telephone was a squeaky one, I think you said?" "Yes, weak and thin, like an old man's." Boyd glanced at his watch--a gold hunter with an inscription. It had been given him by public subscription in Hampstead in recognition of his bravery in capturing two armed burglars in Fitzjohn's Avenue. "It's time we went," he exclaimed; but as we rose Dick entered in hot haste. He had just received Boyd's note and had run round to my office. "I've been out making an inquiry," he said, having greeted us and expressed disappointment at Boyd's decision. "I thought, in order to satisfy myself, and so that I could use the information later on, I would go round to Professor Braithwaite at the Royal Institution and ask his opinion of the scientific apparatus found in the laboratory. I went down to Patterson, got permission to remove it from the house, and took the whole affair in a cab to the Royal Institution." "Well, what's the result?" I inquired breathlessly.