Sub-lieutenant Arnold Hythe was generally regarded as a smart and promising young officer. These golden opinions were gained not by self-advertisement, for the sub was unusually reticent concerning his profession, but by sheer hard work and a consistent application to that great deity that should always be before the eyes of all true subjects of the King--Duty. He held a First-class certificate in Seamanship, Gunnery, and Engineering; a Second in Torpedo, and also in what the Navy List terms "Voluntary Subjects"; he was a qualified interpreter in French and German, and had more than a smattering of Spanish and Italian. In addition to these intellectual qualifications he possessed a powerful physique, and had a sound reputation as an all-round athlete whilst at Dartmouth. The latter portion of his time as midshipman and the first few months after his promotion to sub-lieutenant were spent in duty with the Fifth Submarine Flotilla, whose base was at Fort Blockhouse at the entrance of Portsmouth Harbour. But through some cause, to him quite inexplicable, he had been appointed to the "Ramillies." This was somewhat to the sub’s disgust, but realizing that it was of no use repining over such matters, Arnold Hythe accepted the change with cheerful alacrity. Banks and Moy, the two seamen divers who were also to descend, were already dressed. All that remained was for their copper helmets to be donned, the telephones and air-tubes adjusted, and the glass fronts screwed on. "I don’t expect you will find any actual evidence, and it will be lucky if you come across any circumstantial evidence," remarked Mr. Watterley, the first lieutenant. "But in any case, should you see anything of a suspicious nature, inform us before proceeding to investigate. I need not remind you that the east-going tide is making, and that the current will be running fairly strong in a few minutes." "Very good, sir." Sub-lieutenant Hythe was a diver of considerable experience. Ever since his first descent in the training tank at Whale Island he took naturally to the hazardous duty. Going under the sea had a peculiar fascination for him, whether it was in the hull of a submarine or encased in the cumbersome india-rubber suit and ponderous helmet of the diver. The men at the air-pumps began slowly to turn the handles. The glass front plates of the sub’s helmet were secured, and assisted by a seaman Hythe staggered awkwardly towards the head of the iron ladder. Rung by rung he descended till the water rose to his shoulders. "By Jove, the tide does run," he muttered. "If it’s like this now, what will it be in another ten minutes?"