Slowing the rotors to permit the craft to rise, Tom guided the _Sea Hound_ back to the surface. Then he reversed blade pitch for air flight and gunned the atomic turbines. The seacopter rose steeply above the billowing South Atlantic. Tom radioed a terse report of their experience to the task-force commander and in turn was told that none of the naval craft had either sighted or picked up any sign of a strange sub. As they streaked homeward, Chow was still fuming. "Why don't we post a dummy sub there to scare off the varmints?" "I'll pass the idea along to the Navy," Tom said with a grin. Night had fallen when the searchers arrived back at Fearing Island. Tom cleared with the tower and landed, then went by jeep to base headquarters. He called Enterprises and learned that Bud's condition was improved, and that Mr. Swift had returned that afternoon. He spoke to him about the mystery sub. "This is bad news indeed, son," Mr. Swift said, after hearing how the attacker had defied detection. "You'd better inform Admiral Walter. He had to fly back to Washington." "I'll call him right away," Tom promised. The admiral was equally disturbed when Tom succeeded in reaching him. "We must find that missile as soon as possible--at any cost," he said. "Tom, you Swifts have had considerable experience in undersea dredging. Could you send a team of engineers to assist us in the work?" "Yes, sir," the young inventor replied. "I'll assign men to the job first thing tomorrow." After hanging up, Tom hopped back to the mainland with Chow in a Pigeon Special. This sleek little commercial plane was manufactured by the Swift Construction Company in charge of Ned Newton. Early the next morning Tom and his father drove to Enterprises, and the young inventor plunged into the job of organizing an engineering crew for the missile hunt. Art Wiltessa, a crack underwater specialist as well as engineer, was placed in charge. By noon the group had taken off for the South Atlantic in a Swift cargo jet. A small portable model of Tom's atomic earth blaster was included in their equipment. A jetmarine and a diving seacopter were also dispatched from Fearing to assist in the operations. "It's apt to be a long-drawn-out job--and dangerous," commented Mr. Swift as he lunched with Tom in their office. "Yes. Digging in that silt could be almost as bad as working in quicksand." Mr. Swift's deep-set blue eyes took on a thoughtful gleam. "Speaking of silt, son, I've found the ideal spot for my secret deep-sea farm." "You mean for growing those plants you use in making Tomasite?" Tom asked. The elder scientist nodded. Tomasite, a revolutionary plastic which Mr. Swift had developed, possessed amazing insulating properties against both heat and radiation. One of its secret ingredients came from certain plants found only in Far Eastern waters. Mr. Swift hoped to transplant them locally. "The site is near Fearing Island--about fifty feet in depth," he added.