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 passing 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.

“Stop that!” commanded Trotter, sharply, leaping to grab the spy.

“I only want to say one word to this young scamp!” hissed Lemaire.  “I will not hurt him.”

“You can wager he won’t,” added Captain Jack, clenching his fists and watching the other alertly.  “Let him speak to me, if he wants.”

Trotter thereupon halted, though he watched the Frenchman with lynx-like wakefulness.

Lemaire, however, merely leaned forward until he had placed his lips close to one of the young submarine captain’s ears.

“See here,” hissed the spy, “hold your tongue about everything, and make sure Gaston and myself are released.  Else, no corner of the earth will be a safe place for you.  You can find no place in the world where you will be safe from destruction—­unless you get us out of this one bad fix!”

CHAPTER XXII

Gallant, even to the foe!

“You may have him now,” announced Captain Jack, ironically.  “I reckon he has spoken his piece.”

Trotter’s answer was to leap upon the Frenchman, pinioning his arms behind him.  Packwood snapped handcuffs over the prisoner’s wrists.

“Here is the bullet that Hastings dug out of the tree—­the one that was probably fired at me,” added Captain Jack.  “And here is M. Lemaire’s cane-pistol.  You can see whether the bullet fits the cane.”

Trotter took them, with a swift, admiring look at Benson’s cool, handsome face.

Then, guiding their prisoner, the Secret Service men moved off hastily, for two or three hundred beach walkers had just discovered that something exciting had happened, and were hurrying forward.