Ready for his call were papers of supreme import, and to lose which at the hands of a searching party would be a calamity the secret agent dreaded even to anticipate.
By the air route he had determined to leave, if by any hook or crook Schneider and himself could get hold of an aëroplane.
Billy and Henri had been aloft for several hours, enjoying a bird's-eye view of the really magnificent city, for the possession of which carnage held sway for hundreds of miles.
"Some town this," Billy remarked as he stepped from the machine, completing the sightseeing tour; "after the war I'd like to start a branch factory here."
"Oh, go 'way," laughed Henri, "it would take a derrick to haul you out of Boston or Bangor, once you set foot again in those burgs."
"You forget, old top," suggested Billy, "that we have already on tap a comeback aëroplane trip across the Atlantic. I'm no quitter."
From a coal-laden wagon the contents was being shot into a chute running into the cellar of one of the big houses taken over for officers' occupancy.
One of the grimy heavers, at sight of the boys, came forward to meet them, wiping his hands on the leather apron he wore, removed his fur cap, and took therefrom a scrap of smutty brown paper and tendered it to Billy.
"Guess he wants you to sign a receipt," said Henri, looking over his chum's shoulder.
Billy's glance at the paper set him staring at the man who presented it.