Some month or more had now gone by since the Grey Monk had so startled Bessie Ogden one evening on the terrace. So far as was known, that was the apparition’s first appearance for upwards of twenty years. Now, it was quite evident to Sir Gilbert that if his son had been haunting the place for several weeks, it could only have been with the knowledge and connivance of one or more members of his household. How otherwise could Alec—supposing always that it were Alec—have been supplied with food and lodging? How else could he have had the run of the house at midnight, as the incident of the strong room proved him to have had? Now, Sir Gilbert’s oldest dependent, and indeed the only one left whose memory could go back to so far a period; one, too, whose company had been much sought after by Alec as a youth, was Martin Rigg, the ex-keeper. Martin, who was now over sixty years old, had long been superannuated. Owing to a gunshot wound in his leg, the outcome of a poaching affray, he was a permanent cripple. He and his widowed daughter were now quartered in the old Tower, of which mention was made in the early part of this narrative as being the only remaining portion of the original Chase, the semi-ruinous rooms of which had been specially renovated and fitted up for their occupancy by Sir Gilbert. Linking one thing with another in his memory, the Baronet, by the time he arose, had come to the conclusion that if anybody was more likely than another to be cognisant of his son’s presence at the Chase, that person was Martin Rigg. He breakfasted in his own room, but in order to relieve the anxiety which he knew Lady Pell would feel on his account, he wrote her a brief note and sent it by Trant, in which he told her that, this morning, he felt quite as well as he usually did, that he had a little special business to transact in the course of the forenoon, but that he would not fail to meet her at luncheon. Then after breakfast, he left the house by the back entrance and took his way through the spinny in the direction of the Tower. Even at his slow rate of progression, a few minutes’ walking brought him to it. Grey and stern as he always remembered it, it loomed before him with no visible sign of life about it. That, however, in no wise disturbed him. He did not doubt that he should find either Martin or his daughter, or, more likely still, both of them at home. Going up to the door, which, though of modern make, was of oak and studded with huge square-headed nails, he rapped loudly at it with the ivory knob of his cane; but to his summons even when repeated, there came no response. Then he tried the handle, but only to find that the door was locked. Thus, at the very outset of the inquiry he had been about to enter upon, he found himself unaccountably baulked. CHAPTER XLIII. THE ROOT OF THE MYSTERY