“Wait!” cried M. Lemaire, persuasively, and Benson, halted, looking at him.  “Of course I cannot offer you a lift back to town,” continued the Frenchman, smilingly, “for that would be ungallant.  But Mlle. Nadiboff, who had the pleasure of your company out here will, I know, be most delighted at having your company on the return.”

“Assuredly,” added the young Russian woman, with one of those charming smiles that had failed so utterly with the submarine boy.  “I shall feel most offended if Captain Benson does penance by walking all the miles back to Spruce Beach.”

“I’d be a fool, then, to take that long walk back, when I can ride,” thought Captain Jack.

So he turned, retracing his steps and bowing to the young woman.

“Yet, before we start,” proposed M. Lemaire, anxiously, “let us see, Captain, if we cannot yet come to some arrangement.”

“Well?” demanded Jack, for boyish curiosity tempted him to find how far this Frenchman was willing to go.

“Captain Benson,” proposed Lemaire, “let us say that the price for what I ask shall be fifteen thousand dollars.”

“You’re not getting anywhere near my price, M. lemaire,” laughed the submarine boy, derisively.

“You are playing with me—­laughing at me!” cried the Frenchman, yet he spoke cheerily, for now he began to hope that this American boy might yet be induced to sell himself, body, soul and honor.

“We may as well drop this line of talk,” hinted Jack Benson.  “You were good enough to offer me a ride back to town, I believe?”

“Yet the price?  Let us settle that first,” begged the Frenchman.  “Captain Benson, I will make you one more offer—­but it must be the last.  Listen!”

Yet that word was followed by three or four utterly mysterious words, uttered in a low voice in Arabic.

“Yes,” nodded Mlle. Nadiboff, as Jack glanced from one to the other, “but this must be the last offer.”

“The last, the only, the highest offer,” muttered Gaston, who had recovered from the blow Captain Jack had given him.

“Well, then, Captain Benson, bring me your plans within three days, with all the other data needed for the construction of one of your submarine boats, and I will hand you, in exchange, the sum of twenty thousand dollars.  There you are, my good friend!  Twenty thousand dollars.  Now you are ours, are you not?”

Disgusted, yet crafty, Jack Benson pretended to hesitate.

“You must give me your answer at once,” demanded M. Lemaire.  “I cannot be played with any longer.”

Captain Jack drew himself stiffly erect, looking the Frenchman full in the eyes.

“M.  Lemaire, you must have been a spy for a good many years.  You have been engaged so long in dishonest transactions that you are unable to understand such a thing as common honesty.”

“Do you call it honesty,” demanded the Frenchman, with a bitter smile, “to demand more than twenty thousand dollars for such an easily performed service?”