The Lieutenant-Commander walked from port to starboard and starboard to port thinking pretty hard until the navigating lieutenant came to take charge of the bridge. Of submarines he knew a good deal. He knew that the British navy possessed the very best type of this craft which navigated the under-waters. He had also, of course, read the aerial experiments which had been made by inventors of what the newspapers called airships, and which he, with his hard naval common-sense, called gas-bags with motor engines slung under them. He knew the deadly possibilities of the submarine; the flying gas-bag he looked upon as gas and not much more. The real flying machine he had considered up till a few moments ago as a dream of the future; but a combination of submarine and flying ship such as he and Castellan, if they had not both been drunk or dreaming, had seen a few moments ago, was quite another matter. The possibilities of a thing like that were absolutely limitless, limitless for good or evil, and if it did belong to a possible enemy of Britain, there was only one conclusion to be arrived at--The Isle Inviolate would be inviolate no more. Lieutenant Franklin came on to the bridge and saluted; he returned the salute, gave the orders for changing the course, and went down to his cabin, muttering: "Good Lord, if that's only so. Why, half a dozen things like that could fight a fleet, then go on gaily to tackle the forts. I wonder whether my Lords of the Naval Council will see me to-morrow, and believe me if they do see me." By great good luck it happened that the Commander of the North-eastern District had come up from Hull to Scarborough for a few days' holiday. When he saw the _Cormorant_ steam into the bay, he very naturally wanted to know what was the matter, and so he went down to the pier-head, and met the _Cormorant's_ cutter. As Erskine came up the steps he recognised him and saluted. "Good-morning, sir." "Good-morning, Erskine. What's the matter? You're a little off your ground, aren't you? Of course, there must be a reason for it. Anything serious?" replied the District Commander, as he held out his hand. "Ah, good morning, Castellan. So you've both come ashore. Well, now, what is it?" Erskine took a rapid glance round at the promenaders who were coming down to have a look at the cruiser, and said in a low tone: "Yes, sir. I am afraid it is rather serious; but it is hardly the sort of thing one could discuss here. In fact, I was taking the responsibility of going straight to London with Castellan, to present a report which we have drawn up to the Board of Admiralty." The District Commander's iron-grey eyebrows lifted for the fraction of a minute, and he said: "H'm. Well, Erskine, I know you're not the sort of man to do that sort of thing without pretty good reason. Come up to the hotel, both of you, and let us go into it."