to the transports. If ever
there is an opportunity to get hold of notes or mail delivered to either
of them, don't hesitate to steam it open and copy it."

"Must I?" said Jane. "That hardly seems right or fair."

"Of course it's right," cried Mr. Fleck warmly. "Think of the lives of
our soldiers that are at stake. The devilish ingenuity of these German
spies must be thwarted at all costs. They seem to be able to discover
every detail of our plans. Only two days ago one of our transports was
thoroughly inspected from stem to stern. Two hours later twenty-six
hundred soldiers were put aboard her on their way to France. Just by
accident, as they were about to sail, a time-bomb was discovered in the
coal bunkers, a bomb that would have sent them all to kingdom come."

"How terrible!"

"Somebody aboard is a traitor. Somebody knew when that inspection was
made. Somebody put that bomb in place afterward. That shows you the kind
of enemies we are fighting."

Jane shuddered. She was thinking of the sailing of another transport,
the one that had carried her brother to France.

"Anything seems right after that," she said simply.

"Yes," said Mr. Fleck, "there is only one effective way to fight those
spying devils. We must stop at nothing. They stop at nothing--not even
murder--to gain their ends."

"I know that," said Jane hastily. "I saw something myself you ought to
know about."

As briefly as she could she described the scene she had witnessed in the
early morning hours from her bedroom window, the man following the
younger Hoff, Hoff's discovery and pursuit of him around the corner and
of his return alone.

"And in the morning," she concluded, "they found a man's body in the
side street. He had a bullet through his heart. There was a revolver in
his hand. The newspapers said that the police and the coroner were
satisfied that it was a suicide. I caught a glimpse of Mr. Hoff's face
when he came back from around that corner. It was all convulsed with
hate, the most terrible expression I ever saw. I'm almost certain he
murdered that man. I'm sure it wasn't a suicide."

"I'm sure, too, that it was no suicide," said Mr. Fleck gravely. "The
man who was found there was one of my men, K-19, the man whose badge I
have just given you. He had been detailed to shadow the Hoffs."

CHAPTER IV

THE CLUE IN THE BOOK

Subway passengers sitting opposite Jane Strong as she rode up-town from
Mr. Fleck's office, if they obser