, if he wanted. Jack trusted to his chum,
prowling somewhere about, to have the good judgment to follow the
long-legged fellow away. As for Benson, he didn't mean to do another
thing until he had found the shovel, and had determined just what had
been so carefully buried on this dark night!

So Jack watched, rather indifferently, as Millard slunk off into the
darkness. After three minutes or so had passed, Jack rose and ran
straight for the thicket.

There it was--new ground, that had just been turned over with a shovel.
There was no mound, but the fresh earth showed just where to dig.

"Oh, this is as easy as making change for a blind man!" chuckled the
young submarine skipper, rubbing his hands ecstatically.

What about the shovel? Jack turned to feel around in the darkness.
Really, Millard couldn't be such a very clever fellow! Jack had no
difficulty in finding the shovel. Its handle was sticking out from
under a mass of dead brush.

Jack Benson drew out the implement, brandishing it.

"Hal had the good sense to shadow that chap away," decided the young
skipper. "Otherwise, he'd have been here by this time. Good
haul--rascal and records in the same night. For, if Hal goes on
Millard's trail, then Millard is pretty sure to be a prisoner before
the night is over. Oh, I wish Eph would turn up."

Then Jack took a good grip on the shovel. Clank! spink! spink!

Having been so recently moved, this dirt was easy to dig.

Yet, suddenly, there came a new note on the night air.

"Jack, O Jack!" sounded in Hal's frantic tones. "Quick!"

"Eh?" called Captain Benson. "What's the row? Come here and see what I
can show you!"

"No! You come here--quick!"

"That's queer," pondered Jack Benson, leaning on his shovel, trying to
understand what it could all mean.

Then he heard, even at the distance, the sound of Hal Hastings panting,
as though engaged in hard physical effort.

Again rose Hastings's frantic voice, though somewhat muffled in its
sound.

"If you don't hustle, it will be too late!"

Jack dropped the shovel on the ground, wheeled, and ran down the slope
to where Hal's voice sounded.

"I'm coming, old fellow!" quivered the submarine skipper, starting to
run.

Boom! A terrific explosion shook the ground. The air seemed full of
flying fragments of rock.

CHAPTER X

"MR. GRAY" MAKES NEW TROUBLE

Had Jack Benson started down the slope two or three seconds later he
must have b