There was silence for a few moments, then the female voice inquired--"Are you there?" to which I responded. "You were on a moment ago with 14,982, the public call-office at Putney." "How long was I on?" "About ten minutes." "Have I been on to the same place before this evening?" I asked. "No. Several numbers have been ringing you up, but you haven't replied." "Who were they?" "Oh, I really can't tell you now. It's quite impossible. I remember that the call-office at Piccadilly Circus was one, and I think the one in the Minories." "They were all call-offices--no private persons?" "I'm unable to say. I've been on duty for the past four hours, and have connected up thousands of numbers." "Then you can't tell me anything else?" I asked disappointedly. "No. I'm sorry I can't," replied the girl. I was about to place the receiver on its hook when a sudden thought occurred to me, and again I addressed her. "This matter is a most urgent one," I said. "Can't you ask at the call-office for a description of the man who has just been speaking?" "There's no one there. It is merely an instrument placed in a passage leading to some offices," was the reply. I hung up the receiver, and turning to Patterson repeated the conversation. "Extraordinary," he ejaculated, when I had concluded. "We must keep that appointment. The inquiry is plain proof that murder has been committed, and further, that more than one person is in the secret." "But is it not strange that this person, whoever he is, should dare to telephone in that manner?" "It certainly is a bold move," my companion answered, "but from his conversation it is evident that the assassin promised to telephone to him, and was either disturbed in his work and compelled to escape hurriedly, or else forgot it altogether. Again, it's plain that to avoid detection the unknown man went from one call-office to another, always ringing up to this house, and never obtaining a response until you answered." "His inquiry was certainly a guarded one." "And your answers were smart, too," he laughed. "You were careful not to commit yourself." "Do you think he'll keep the appointment?" I asked eagerly. "That remains to be seen," answered my friend, glancing at the bull's-eye to see if it were burning well. "If he's not a blunderer he won't." "Well, let's hope he does," I said. "You would arrest him, of course?" "I don't know," he answered doubtfully. "We might learn more by keeping observation upon him for a day or two." "Well," I said, "we haven't yet searched the place thoroughly. Let's see what is above."