By jeep and truck, Tom's group sped across the island to the dock. Exman was quickly lowered aboard through the sub's hatch. The others followed, the conning-tower hatch was dogged shut, and soon the _Swiftsure_ was gliding off into the shadowy blue-green depths. "What's your sailing plan, skipper?" Hank Sterling inquired. The quiet-spoken, square-jawed engineer stood beside Tom at the atomic turbine controls and looked out through the transparent nose of the jetmarine. "Go slow. Give 'em plenty of chance to pick up our trail," Tom replied. For two hours they cruised at moderate speed. Nothing happened. Disappointed, Tom surfaced and radioed his father for news, after cutting in the automatic scrambling device. "You're in time for an exciting flash," Mr. Swift reported jubilantly. "What is it, Dad?" "An attempt to earthquake New York has just failed!" Grins broke out on the faces of the crew as they heard Mr. Swift's words come over the loud-speaker. Bud let out a happy whoop. "That's great, Dad!" Tom said. "Maybe we've got 'em licked on the quake front. No luck so far, though, on our new project." "Well, keep in touch and let me know at once if anything happens," Mr. Swift urged. "Right, Dad!" Tom promised. Again the _Swiftsure_ submerged. This time it was only a few minutes before Arv Hanson gave a cry of warning. "Something on the sonarscope, skipper!" Bud, Hank, and Chow hastily gathered around the scope to watch. The blip grew larger rapidly. It was clearly another submarine, closing in on a collision course. Tom put on a burst of speed, as if attempting to outrace their pursuer. But he was careful to gauge his knots by reports from the sonarscope, in order not to widen the gap between the two craft. There seemed no danger that this would happen, although the _Swiftsure_ raced ahead faster and faster. Still the enemy sub continued to close in like a marauding shark, finally passing Tom's craft. "Some baby!" Bud muttered respectfully. The words were hardly out of his mouth when a missile streaked across their bow, in plain view through the _Swiftsure's_ transparent nose. Its foaming wake rocked the jetmarine. "They're attacking us!" Bud cried out. Tom slammed shut the turbine throttle, bringing his craft to a gliding halt in the water. At the same time, he switched on the sonarphone. "Orders to Swift sub!" a voice barked over the set. "Surface and heave to! No tricks, or the next missile will not be across your bow!" Tom blew his tanks and sent the _Swiftsure_ spearing upward. As the conning tower broke water, Tom and his men swarmed up on deck. Seconds later, a sleek gray enemy submarine knifed into view. Its hatch opened and several men climbed out. To Tom's amazement, their leader was Samson Narko! Chow let out a yelp of rage. "Why, you sneakin', double-dyed, bushwhackin' polecat!" the old Westerner bellowed. "We shoulda kept you hawg-tied, 'stead o' lettin' you go free!"