“A book code,” Jane repeated perplexedly.  “I don’t understand.”

“It is very simple when two persons who wish to communicate with each other secretly both have a copy of some book they have agreed to use.  They write their message out and then go through the book locating the words of the message by page, line and word.  That’s what the three columns mean.  Our only problem is to discover which is the book they both have.  They often employ the Bible or a dictionary or—­”

He stopped abruptly and studied the columns of figures.

“This code,” he went on, “on its face is from a book that has at least 544 pages.  One of the pages has at least 76 lines—­that’s the middle column—­so the book must be set in small type.”

“What book do you suppose it is?” asked Jane interestedly.  She was glad now that she had listened to Carter.  She was sure she was going to like being in the service.  It was all so interesting, and she was learning so many fascinating things.

“If my theory is right those letters indicate that the book used was an almanac.  That’s the book that Wilhelmstrasse made use of when a wireless message was sent in cipher to the German ambassador directing him to warn Americans not to sail on the Lusitania.  They betrayed themselves at the Embassy by sending out to buy a copy of this almanac.  Let’s see how our theory works out.”

Taking up an almanac that lay on his desk he began turning to the pages indicated in the first column of figures, checking off the lines indicated in the second column and putting a ring around the words marked by the third column of figures.

“Let’s see—­page 534—­fifth line—­second word—­that’s (eight).  Now then—­page 331—­that’s the chronology of the war in the almanac, so I guess we are on the right track—­fifty-fourth line—­sixth word—­(transport).”

“Isn’t it wonderful!” cried Jane.

“Damn them,” he exploded.  “I know we are on the right track.  Some transports with our troops sailed this morning, and already the German spies are spreading the news, hoping to get it to one of their unspeakable U-boats.”

Quickly he ran through the rest of the cipher, writing it out as he went along: 

Eight—­transport—­sa
iled—­Thursday—­15,000—­infantry—­five destroyers.

As Fleck finished the message his face became almost black with rage.

“Damn them,” he cried again, “in spite of everything we do they get track of all our troop movements.  Their information, whenever we succeed in intercepting it, is always accurate.  If I had my way I’d lock up every German in the country until the war was over, and I’d shoot a lot of those I locked up.  Until the whole country realizes that we are living in a nest of spies—­that there are German spies all around us, in every city, in every factory, in every regiment, on every ship, everywhere right next door to us—­this country never can win the war.”