going on in our shipyards and munition shops may get through to the
enemy. We can't prevent his agents from getting information--that is
always possible to those with unlimited command of money, for there
are always swine among workmen, and among higher folk than workmen,
who can be bought. You may take it as certain that little of
importance is done or projected in this country of which enemy agents
do not know. But their difficulty is to get it through to their
paymasters, within the limit of time during which the information is
useful. There are scores of possible channels, and it is up to us to
watch them all. You have already shown some grasp of our methods,
which in a sentence may be described as unsleeping vigilance. Once we
know the identity of an enemy agent, he ceases to be of any use to the
enemy, but becomes of the greatest value to us. Our motto is: Ab hoste
doceri." He pronounced the infinitive verb as if it rhymed with
glossary.

"You are quite a scholar, Mr. Dawson," remarked I politely.

"Yes," said he, simply. "I had a good schooling. I need not go into
details," he went on, "of how we watch the correspondence of suspected
persons, but you may be interested to learn that during the three
weeks which I have passed in your city all your private letters have
been through my hands."

"The devil they have," I cried angrily. "You exceed your powers. This
is really intolerable."

"Oh, you need not worry," replied Dawson serenely. "Your letters were
quite innocent. I am gratified to learn that your two sons in the
Service are happy and doing well, and that you contemplate the