"Never sir," replied Jack. "We have seen considerable of Navy life, but this is the first time we've ever been at a fort." "You don't see much about this place, do you," laughed the engineer officer, "that makes you think of a fort?" "Not much," Benson admitted. "Yet we have a fighting plant here that could prevent a big fleet, indeed, from getting far up the bay at the important cities beyond. That is," Woodruff continued, thoughtfully, in a low voice, "if the enemy, in advance of his coming here, doesn't know all about our defenses through the work of spies." Just at the point near the dock, Fort Craven looked not unlike the yard of a big factory plant. Wagons going and coming constantly heightened this effect. Beyond, past the plain, on one side, Major Woodruff pointed out the barracks of the Coast Artillery, of the Engineers soldiers, and of the Infantry. There were also laborers' quarters, several office buildings, a hospital, a chapel, and two streets of cottages that served as quarters for the officers stationed at Fort Craven. It was into one of these officers' streets that Major Woodruff soon led his three young companions. Admitting the boys to his home, the major took them to the library on the ground floor. "Now, I'll telephone for Lieutenant Ridder to come over in citizen's dress," announced the major. "At the same time, I must advise Colonel Totten, who is commander of the post. He may come over here, or he may order us all over to headquarters." Colonel Totten elected to come over to the major's quarters. He arrived just after Lieutenant Ridder, who proved to be a rather boyish looking young man, not long out of West Point. The plans were quickly laid by which Lieutenant Ridder was to take an automobile up to Radford, going to one of the hotels and registering. Jack and his two chums were to make the journey in another auto. They would go to still other hotels, perhaps to three different ones. At any moment when instructions were needed, any one of the three could call up Lieutenant Ridder on the telephone. In addition, Major Woodruff gave each of the three submarine boys a written and signed authorization for them to call upon the police to seize Millard, if found, and hold the fellow for the United States military authorities. "Now, you young men may start for Radford," continued the major. "Colonel Totten and I will busy ourselves with the despatches that must be sent to Washington about this affair. But I trust, lads, you will not fail to realize the importance of prompt success." "It's a special duty to the Flag, sir," Captain Jack answered, simply. The automobiles were waiting outside. Lieutenant Ridder was given a three minutes' start. Then the submarine boys followed after, in a second car. As Radford was but four miles distant from the post the trip was not to be a long one.