"YOU see," Dave nodded to his brother officers, "the theory we had worked out about the method of supplying mines to the submarine layers was the right one. I think that we shall be able to show some results to the admiral." Dan was then instructed to remain to keep watch over the shoals, while the "Grigsby" soon afterwards started for port, escorting the two prizes. Before daylight the captured under-sea boats were duly turned over to the British authorities. Darrin then sought the admiral, and, despite the lateness of the hour, he was soon admitted. "What do you need for your enterprise?" inquired the admiral after listening attentively to the plan Dave had unfolded to him. "Nothing but a dirigible, commanded by the right man," Dave explained. "That ought not to be difficult," declared the British officer. "You shall have what you want. Now, suppose we go over the chart, to make sure that I understand just what you propose to do." On the map Darrin traced the course that he felt sure the German underseas craft pursued when bringing cargoes of mines to the other submarines that were laying mines in British waters. "That would be the natural course for such craft to take," agreed Admiral Wheatleigh. "I trust that you are right in your surmises. If you are, we should have some excellent results within the next few days." "I shall know, sir, within forty-eight hours, and I think it likely that the enemy will also hear something about it within the next few days. At least, sir, the German admiralty should be able to guess." Dave took his leave, hastening back to the "Grigsby," which, an hour later, weighed anchor and stood out to sea. By that time Dave was sound asleep, for he had been through a great deal and was sorely in need of rest before he reached the scene of his intended activities. Some hours later he was called, and was soon on the bridge. "You are at the point at which you wished to be called," said Fernald when Dave reached the bridge. "And you will do well to seek your own rest now, Mr. Fernald," Darrin answered. "You can be called, if needed." Half an hour later Darrin made out, in the sky astern, a tiny speck that rapidly came closer, and proved to be the dirigible sent at his request. As the dirigible came nearer signals were rapidly exchanged. The course for the aircraft was made plain. As for the "Grigsby," her speed was slowed down to mere headway and she loafed over the waters. Two hours passed during which the "blimp" aloft sailed rapidly to and fro in the sky, zig-zagging over the course in a way that covered several square miles in an hour. "She's found something, sir!" cried Ensign Andrews. "She has sighted a craft, bound over the course we had suspected," said Darrin, as signals broke out rapidly from the car under the big gas bag. "We'll let the submarine get by us before we start in chase."