Halliday was convinced that in this way the miracle of Mrs. Jarsell had taken place. No other means of transit could have landed her at the place where Durwin had met with his death. Of course, this assumption intimated that Mrs. Jarsell was an accomplished aviator, and that there had been no hitch in the journey from Sheepeak to Blackheath. But these were not impossibilities, for Vincent probably had taught the woman how to fly, and perhaps had handled the machine himself. There was room for two in the aeroplane, as Dan very well knew, since he had taken Penn for a flight himself, and the vehicle used was probably built on the same lines as the one lent. Since aviation was yet in its infancy, there was certainly a possibility that such a journey could not take place without accidents or hindrance. But, as inferior machines had accomplished greater distances, Dan quite believed that Mrs. Jarsell, with or without Vincent as pilot, had reached London in one smooth stretch of flying. On other occasions she might not have been so successful, but on this one she probably had, for to get to Blackheath in time to commit the crime, it would have been necessary for her to use rightfully every second of the given time. No wonder with such a means of transit at her disposal she could prove an advantageous alibi, when occasion demanded. Also, since the late conquest of the air afforded her the opportunity of swift travelling, greatly in excess of other human inventions, it was quite reasonable that she should live so far from the scene of her criminal exploits. Thinking thus, Halliday stumbled across the very person who was in his thought. He rushed with bent head along the roads and unconsciously mounted towards the vast spaces of the moorlands, stretching under gray skies. Thus--and he swiftly decided that the collision was meant--he ran into Mrs. Jarsell, who approached in the opposite direction. She laughed and expostulated, as if Dan was in the wrong, although she must have seen him coming, and the road was wide enough for her to move to one side. "Really, Mr. Halliday, you require the whole country to move in," said Mrs. Jarsell in her heavy way, and with an affectation of joviality. "I--I--I beg your pardon," stammered Dan, not quite himself, and stared at her as though she had suddenly risen out of the earth. Indeed, so far as he was concerned, she had done so, ignorant as he was of her approach. The woman was arrayed in her favorite white, but, as the day was chilly, she wore a voluminous cloak of scarlet silk quilted and padded and warm both in looks and wear. Her black eyes, set in her olive-hued face, peered from under her white hair as watchfully as ever. At the present moment, her heavy countenance wore an expression of amusement at the startled looks of the young man, and she commented on them with ponderous jocularity.