All three of the submarine boys were laughing so heartily, as they entered the shipbuilder's private office that Jacob Farnum, a youngish looking man to be at the head of so large a manufacturing plant, glanced up quickly. "What's the joke, boys?" he asked. "I haven't had a laugh since I pounded my thumbnail with a sledge-hammer." Captain Jack Benson quickly detailed the meetings with Radberg and d'Ouray. "The Frenchman didn't look a bit like a 'shovelee' either," muttered Eph. "If anything, that looked more in the German's line." "Well, you'll have a chance to get rid of nonsense, now, for a while," went on Mr. Farnum, after having enjoyed a few laughs with the boys. "I've some serious business in hand for you, and the time has come." That was like the shipbuilder. Whatever he was planning, at any time, he kept strictly to himself until the time came to put the plan into operation. "There's quite an important little job for you up at Craven's Bay," continued Mr. Farnum. "You know, there are important fortifications there, because the Navy people expect, in wartime, to use Craven's Bay as a possibly important naval station and shelter for vessels that have to put in. Now, for some time the Army engineer officers have been perfecting a system of submarine mines for the bay. The engineers have a problem on hand as to whether an enemy's submarine boats could sneak into the bay and blow up the submarine mines before the Army woke up to the danger." "There's a chance that _that_ could be done," nodded Jack, musingly. "Jest so," nodded Mr. Farnum. "So I want you to go up in one of the boats. To-morrow the engineer officers at that station will test it out with you whether a submarine can destroy the mines, or the mines could be made to destroy the submarine boats." "Then the Army engineer officers will use dummy submarine mines, I hope," broke in Eph. "Oh, of course," nodded Mr. Farnum. "Now, the trip to Craven's Bay is only an eight-hour sail at a good gait, so you won't really need to start until after dark to-night." "I believe I'd rather start now, though, and go at less speed," suggested Jack, thoughtfully. "That's just as you please, of course," nodded the shipbuilder. "It will take us out on the water, for one thing," Captain Jack continued, "and we've been growing stale on shore, of late." Then he added, whimsically: "Besides, if the agents of any more foreign governments show up, they won't find us here." "And there's a Jap just about due now," grimaced Eph. "Take Williamson with you, for use in the engine room," advised Mr. Farnum. "That will allow you to take the boat through with two watches above and below. Which boat will you take?" "The 'Spitfire,' unless you'd rather have us take the other one," young Benson replied. "Take the 'Spitfire,' by all means," nodded the owner. Twenty minutes later, Williamson having been found, the crew was all ready for the start for Craven's Bay.