His escaped prisoner had turned the key on the outside. He was locked in his own study!
Momentarily nonplussed, he stood looking at the closed door. The sound of a restarted motor from outside the house spurred him to action. He switched off the lamps, crossed the darkened room and drew back the curtain, throwing open the French windows. Brilliant moonlight bathed the little lawn with its bordering of high privet hedges. Stuart ran out as the sound of the receding car reached his ears. By the time that he had reached the front of the house the street was vacant from end to end. He walked up the steps to the front door, which he unfastened with his latch-key. As he entered the hall, Mrs. M'Gregor appeared from her room.
"I did no' hear ye go out with Miss Dorian," she said.
"That's quite possible, Mrs. M'Gregor, but she has gone, you see."
"Now tell me, Mr. Keppel, did ye or did ye no' hear the wail o' the pibroch the night?
"No—I am afraid I cannot say that I did, Mrs. M'Gregor," replied Stuart patiently. "I feel sure you must be very tired and you can justifiably turn in now. I am expecting no other visitor. Good-night."
Palpably dissatisfied and ill at ease, Mrs. M'Gregor turned away.
"Good-night, Mr. Keppel," she said.
Stuart, no longer able to control his impatience, hurried to the study door, unlocked it and entered. Turning on the light, he crossed and hastily drew the curtains over the window recess, but without troubling to close the window which he had opened. Then he returned to the writing-table and took up the sealed envelope whose presence in his bureau was clearly responsible for the singular visitation of the cowled man and for the coming of the lovely Mlle. Dorian.
The "pibroch of the M'Gregors": He remembered something—something which, unaccountably, he hitherto had failed to recall: that fearful wailing in the night—which had heralded the coming of the cowled man!—or had it been a signal of some kind?