"That was a shot!" guessed the submarine boy, like a flash, and in the next breath he muttered: "Aimed at me, too!"

Jack pitched forward, falling upon his face. If one shot had been fired, another might be as soon as the unknown marksman realized that he had missed.

Several people, near by, fancied they had heard a shot, and turned, curiously. Then, as soon as Benson was espied lying on the ground a rush was made in his direction.

At that moment Hal Hastings happened to be looking over toward the beach.

Like a flash he was up and away, his magazine falling from his lap to the ground.

"Now, what on earth has taken Hastings off like that?" demanded Mr.

Farnum, looking around in surprise. "There are other people running, too. Come along, Dave!"

Hal shot his way through the rapidly gathering crowd. He reached Jack Benson just as the latter leaped up, laughing.

"Why all this excitement, just because I stubbed my toe against a dew-drop and fell?" demanded Benson, laughing.

"Weren't you shot?" gasped Hal.

"If I was, I'll make the rascal prove it," asked back Captain Jack.

"But, now you mention it, I think the tree _was_ hit."

Jack turned and looked the tree trunk over at about the height of his own head from the ground.

"See here," he remarked, laying a finger on a small perforation in the bark, "I think a bullet, or something of the sort, went in here."

"We'll soon find out then," proposed Hal, whipping out his jack-knife, opening a blade and beginning to dig. The crowd grew in size. Messrs.

Farnum and Pollard had great difficulty in forcing their way through.

After some time spent in patient work Hal dug out a steel-jacketed bullet, short and of small calibre.

"You want to find the man with a weapon that bullet fits, and then make it warm for him," advised one man in the front rank of the crowd.

"Why?" queried Captain Jack, coolly, examining the missile, then dropping it carelessly into his pocket. "Some fellow fired an accidental shot, very likely, and is at this moment the most scared man at Spruce Beach.

What's the use of jumping on anyone just because he had a moment of carelessness?"

"That's right, young level-head!" nodded another man, approvingly.

Messrs. Farnum and Pollard hung back somewhat. They were near enough to hear and see, and they had their instant suspicions. But the crowd knew nothing of the spy outrages, and it was not necessary to inform strangers.

So, within a few minutes the crowd broke up, straying off in quest of something more interesting. The submarine party kept on up to the hotel porch.

"That was a revengeful move, pure and simple," declared Jacob Farnum, in a low voice.

"Of course," a.s.sented Jack. "It's going to be something of a task though, to find out, for certain, just who fired that shot."

Even as the four stood there on the veranda a door opened, and M.

Lemaire, faultlessly attired for an afternoon stroll, stepped out.

"Ah, good afternoon, gentlemen," was his unconcerned greeting, as he recognized the quartette.

This French spy had evidently dressed himself with a good deal of care.

He carried himself with much precision and lightly twirled a natty cane.

"Pardon me, monsieur," spoke Jack, stepping forward, and looking past the Frenchman; "is that one of your friends down the road?"

As the Frenchman turned to look, young Benson swiftly and adroitly took his cane from him.

Like a flash, his eyes full of fire, Lemaire heeled about, then leaped at the young submarine captain.

But Hal Hastings stepped between them so neatly that the Frenchman collided with him instead.

"Hold this fellow a moment, please," requested Captain Jack. "I've found something interesting."

Hal Hastings grabbed Lemaire's right arm. Jacob Farnum instantly possessed himself of the other. David Pollard sprang forward so that he could take a hand, if need be.

Captain Jack stood holding the spy's walking stick, ferule end upward.

It was a rather long, slender-looking ferrule of steel. But what interested young Benson most was that he had found that the ferrule was hollow.

Quickly the submarine boy examined the rest of the cane.

"Release me! Hand that stick back to me!" hissed the Frenchman. "Oh, some one shall pay for this unpardonable outrage!"

But Hal and Mr. Farnum only gripped the spy the more tightly.

"I believe I've found out something," announced Jack, in a low voice.

"Wait a second or two."

He had come upon a concealed spring near the head of the cane. Stepping to the edge of the porch, the submarine boy pointed the ferrule end at the ground, then pressed upon the spring.

A sharp, though not loud report followed, and a bullet plowed into the ground. There was a flash at the end of the ferrule, though but a barely perceptible amount of smoke.

"So, M. Lemaire, you carry a pistol cane, that uses smokeless powder and shoots steel-jacketed bullets?" inquired Jack, turning to the prisoner, who, white-faced, stood gnashing hi's teeth in helpless rage.

"I wonder if the bullet Hastings dug out of the tree trunk will be found to fit this weapon?"

"You miser-r-r-rable dog!" screamed Lemaire. "Thief! Liar!"

"Oh, keep cool about it, do," urged Jack, smilingly.

"What's this?" demanded Trotter, suddenly appearing on the scene.

Packwood was just behind him.

Jack swiftly told what had happened, and what he had just discovered, at the same time pa.s.sing the cane to the Secret Service man.

"Lemaire, I guess you'd better come with us, for safe-keeping," advised Trotter, dryly.

"You ar-r-rest me?" snarled the Frenchman.

"Oh, yes; if you insist upon a name for it."

M. Lemaire's face looked uglier than Jack had ever dreamed it possible for a man's face to look. As Hal and Farnum let go his arms the spy took a quick step toward Jack Benson.