“What does the ‘97’ at the end mean?” questioned Jane timidly, a little bit frightened at his outburst, yet more than ever realizing the vast importance of his work—­and hers.

“Oh, that’s nothing.  Probably old Hoff’s number.  Most spies are known just by numbers.”

“Yes, of course,” said Jane, flushing as she recalled that she herself was now “K-19.”  Was she a spy?  Was Mr. Fleck a chief of spies?  She always had looked on a spy as a despicable sort of person, yet surely the work in which they both were engaged was vital to American success at arms—­a patriotic and important service for one’s country.

“I suppose,” she said thoughtfully, unwilling to pursue the chain of her own thought any further, “that there is evidence enough now to arrest old Mr. Hoff right away.”

“You bet there is,” said Mr. Fleck emphatically, “but that is the last thing I am thinking of doing yet.  He is only one link in a great chain that extends from our battleships and transports there in the North River clear into the heart of Berlin.  We’ve got to locate both ends of the chain before we start smashing the links.  We’ve got to find who it is in this country that is supplying the money for all their nefarious work, from whom they get their orders, how they smuggle their news out.  Most of all we have got to find where the end of the chain is fastened in our own navy.  The traitors there are the black-hearted rascals I would most like to get.  They are the ones we’ve got to get.”

“Yes, indeed,” assented Jane, suddenly recalling the navy lieutenant she had seen in the Ritz chatting so confidentially with old Otto Hoff’s nephew.  Was he, she wondered, one of the links in the terrible chain?  Was he the end—­the American end of the chain?

“We’re certain about the old man now,” said Fleck, rising as if to indicate that the interview was at an end.  “We’ve got to get the young fellow next.  There is nothing in this to implicate him.  That’s your job.  Find out all you can about him.  Get acquainted with him, if possible.  That’s one of the weakest spots about all German spies.  They can’t help boasting to women.  Try to get to know this Fred Hoff.  It’s most important.”

“I’ll do more than try,” said Jane spiritedly.  “I’ll get acquainted right away.  I’ll make him talk to me.”

CHAPTER V

ON THE TRAIL

Few men, even fathers, realize how utterly inexperienced is the average well-brought-up girl, just emerged from her teens, in the affairs of the great mysterious world that lies about her.  A boy, in his youth living over again the history of his progenitors, escapes his nurse to become an adventurer.  At ten he is a pirate, at twelve a train robber, at fourteen an aviator, actually living in all his thoughts and experiences the life of his hero of the moment, learning all the while that the world about him is full of adventurers like himself, ready to dispute his claims at the slightest pretext, or to carry off his booty by prevailing physical force.