"More than that: the war will be lost, and with it the Fatherland, unless these two spies are seized and destroyed.
"The Great Secret of Germany is in danger.
"To possess themselves of it—for already they suspect its nature—and to expose it not only to the United States Government but to the entire world, is the mission of these two enemy agents.
"If they succeed it would mean the end of the German Empire.
"If our understanding with a certain neutral Power be made public, that also would spell disaster for Germany.
"The situation hangs by a hair, the fate of the world is suspended above the forest of Les Errues."
On the 14th the process of infiltration began. But the Hun invasion of Les Errues was not to be conducted in force, there must be no commotion there, no stirring, no sound, only a silent, stealthy, death-hunt in that shadowy forest—a methodical, patient, thorough preparation to do murder; a swift, noiseless execution.
Also, on the 14th, the northern sky beyond the Swiss wire swarmed with Hun airplanes patrolling the border.
Not that the Great Secret could be discovered from the air; that danger had been foreseen fifty years ago, and half a century's camouflage screened the results of steady, calculating relentless diligence.
But French or British planes might learn of the presence of these enemy agents in the dark forest of Les Errues, and might hang like hawks above it exchanging signals with them.