with docks. Here the recovery
tugs and fuel tankers were moored, as well as the Swifts' fleet of
undersea craft.

Tom had chosen a cargo-hauling jetmarine, named the _Swiftsure_. It was
a larger version of his original two-man jet sub, the _Ocean Dart_. He
had given orders the night before to have it ready for sea by morning.

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_ t