He laughed merrily, now, and Mlle. Nadiboff turned away her head to conceal the tears of vexation that started to her eyes.

“Bah!” she thought to herself.  “I have been wasting time—­at Lemaire’s orders.  The only way to induce this boy to betray his trust will be by offering him presents of marbles, tops, kites—­bah! Bah!”

Mlle. Nadiboff settled back in her seat, looking straight ahead, her attitude as frigid as could be.  For some moments she did not attempt to speak.  When she did open her lips she said, icily: 

“I find that I have been wasting my time.”

“Wasting your time, Mademoiselle?” echoed Jack Benson, coolly, for he was much more fully alive to the situation, thanks to Mr Graham, than she had any chance to know.  “May I ask what you have been trying to do?”

The question made the young woman bite her lip.  Mlle. Nadiboff had been a spy quite as long as Mr. Graham had stated.  As she looked back over the years she was able to recall man after man whom she had flattered and lured by the witchery of her eyes.  Secret after secret she had coaxed from men entrusted with guarding such mysteries.  The rewards of the work had kept M. Lemaire and herself both bountifully supplied with money by the foreign governments that they had served as spies.  Most men whom she had tried to win into her service the young Russian woman had found easy enough victims.  But now, here was a sixteen-year-old boy laughing at her attempts at “cleverness.”

“I was wrong to think Jack Benson a fool,” she said to herself, angrily.  “He is far more clever than the men I have met.  I can do nothing with him.  I must turn him over to Lemaire—­to see if that prince of spies, as he has often been called, can find the flaw in this submarine boy’s armor.”

With that Mlle. Nadiboff leaned forward, murmuring a few words to the chauffeur, who nodded slightly.  Then the young woman leaned back, turning a smiling, friendly but no longer coaxing face to Jack Benson.

“If I have amused you,” she smiled, “I am glad.  We will say that much and forget the rest, eh, Captain Benson.”

“I am glad to agree to anything that will please you,” responded the boy, gravely.

Mlle. Nadiboff shot a covert look at his face, then decided to say nothing.  She began to have a suspicion that this sixteen-year-old boy was far more clever than she, despite all her years of strange experiences.

A mile further along the automobile branched off the main road, running down a shaded lane at much reduced speed.

“What is this—­some short cut back to the beach?” asked Jack, trying to conceal his astonishment.

“Yes,” replied the young Russian, falsely.

Soon the big car stopped.  The chauffeur thrust a whistle between his lips, blowing a trilling blast.

Jack Benson changed color somewhat.  This sounded suspicious—­a signal in the woods.  It was doubly suspicious after the hints that Mr. Graham had given the young submarine captain.