The following day Lady Cookham and the children left, and Sir George finding himself the sole occupant of the house, the servants having left at midday, telephoned to Sydney N. Morgan, a well-known private detective who specialised in cases of theft and blackmail, asking him to come. On his arrival at "The Mayfields" that same evening, Morgan listened to all Sir George had to say, and then made an exhaustive examination of the premises, paying particular attention to the cupboard in the hall. "Well?" Sir George asked. "What is your opinion? Rats?" "Not human ones, at any rate," Morgan replied. "Anyhow, I can find no traces of them. I incline to your theory of nerves." "Imagination first and then suggestion." Sir George grunted. Now that he was alone there with the detective, he began to have misgivings. The house seemed strangely large and silent. But ghosts! Bah! There were no such things. He said as much to Morgan, and they both laughed. Then they stared at one another in amazement, for, from afar off, there came an answering echo, a faint yet distinctly audible--chuckle. They were standing at one end of the corridor on the ground floor when this happened, and to both of them the sound seemed to emanate from the cupboard. "What was that?" Sir George asked. "The wind?" "It may have been," Morgan said dubiously, "but there's no getting away from the fact that it was a queer noise for the wind to make. I made sure I looked everywhere." "I'll go upstairs and get my revolver," Sir George observed. "It may come in handy. Will you remain here?" They looked at one another furtively, and each thought they saw fear in the other's eyes. Both, however, had reputations to sustain. "I'll wait down here, Sir George," Morgan said, "and keep an eye on the cupboard. You'll call if you want me." "I will," Sir George replied. "I shan't be gone more than a minute. Be on your guard. It's just about this time the alleged disturbances begin." He hurried off, and Morgan watched his long legs cross the hall and hastily ascend the main staircase. The hall occupied a large space in the centre of the house, and overlooking it was a gallery connecting the east and west wings.