et him when we built the submarine
'Advance'--you boys remember her--but I can't seem to recall his name.
Let me see--Ha! I have it! Britten! That's it, John Britten, the best
salvage man on the coast!"

"Maybe he's busy too," said Ned, "as all the others seem to be."

[Illustration: "Maybe He's Busy, Too."]

"I think not," replied the elderly scientist, "because he's retired.
Yet I believe he'll undertake the job if I ask him as I once did him a
great favor. His salvaging outfit is in Florida, but he lives on
Delaware Bay. I'll phone him at once."

"That's great, Dad!" cried Tom, his face lighting up with renewed hope.
"Tell him I'll bring him here by plane tomorrow. We can talk things over
and start for Florida from here."

"He'll go," said Mr. Swift a few minutes later, turning away from the
telephone with a smile. "Said he'll be tickled to get back in
harness."

[Illustration: "He'll Go," Said Mr. Swift]

"Thanks a million, Dad! You've saved the day!"

The following morning the boys hurried out to the Swift private airport
to oversee the fueling of the huge plane Tom had decided to take. At
first he had thought of making the trip in his small two-seated racer,
since it was the fastest craft in the hangar. Realizing, however, that
Captain Britten might want to bring along considerable baggage, the
young inventor had told Ned he felt it best to go in his flying boat.

[Illustration: They Fueled the Huge Plane]

The "Winged Arrow," in which Tom once had made a memorable rescue flight
to Iceland, was equipped now with a retractable landing gear as well as
with pontoons, enabling the craft to descend on both land and water.
Suddenly Tom became very excited as he looked at the hydroplane.

"Look, Ned!" he cried. "Can you beat that!"

[Illustration: "Look, Ned," Tom Cried]

CHAPTER V

IN PERIL

Upon inspection, it was found that three half-inch holes had been
drilled into each pontoon. It was evident that only an enemy of Tom or
of the Swift Company could have done such a thing.

"Ned, that proves it!" declared the young inventor gloomily.

[Illustration: Three Holes in Each Pontoon]

"Proves what?" Ned asked.

"Can't you see? It all ties in with Mr. Damon's so-called relatives, and
their knowledge of my formula for a bendable glass. Someone in our shops
is a traitor--or worse!"

"But what has a damaged hydroplane to do with that?" objected Ned.

"If we had landed on water with these dama