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 been killed.

As it was, the fearful force of concussion sent him sprawling headlong on the ground.

A shower of small fragments of rock and of loose dirt fell about him.

Yet Jack was up again, like a flash, never stopping to inquire whether he had been hurt.

“O-oh!” came the groan, from Hal Hastings.

“There, in a second!” panted Captain Jack, beginning to run again.

A blow sounded, then a fall.

Captain Jack raced into a little, bush-lined hollow, just in time to see Millard leap up and take to his heels.

Hal Hastings lay on the ground, as though badly hurt.

“Oh, you would, would you?” raged Captain Jack Benson, making a swift spurt after Millard.

He caught the long-legged one, too, by the back of the fellow’s coat collar.

Yank!  Millard was pulled over backward.  Down he went, Benson piling a-top of him.

“Down!” cried Skipper Jack, exultantly.  He found, however, that Millard possessed strength enough to put up a stiff fight.

“Come on, Hal—­if you can!” called Jack Benson, sharply.

“Can’t—­just yet,” came, in muffled tones, from the usually prompt Hal Hastings.