IS MAINLY MYSTERIOUS. "A womanperhaps?" "Who knows! Poor Dick Harborne was certainly a man of secrets, and of many adventures." "Well, it certainly is a most mysterious affair. You, my dear Barclay, appear to be the last person to have spoken to him." "Apparently I was," replied Lieutenant Noel Barclay, of the Naval Flying Corps, a tall, slim, good-looking, clean-shaven man in aviator's garb, and wearing a thick woollen muffler and a brown leather cap with rolls at the ears, as he walked one August afternoon up the village street of Mundesley-on-Sea, in Norfolk, a quaint, old-world street swept by the fresh breeze of the North Sea. "Yesterday I flew over here from Yarmouth to see the cable-laying, and met Dick in the post-office. I hadn't seen him for a couple of years. We were shipmates in the Antrim before he retired from the service and went abroad