In July he came home, not empty-handed. The honor of receiving the first contract had been awarded to the Waite Motor Company and Potter carried it, a sacred treasure, buttoned against his breast. Then began in earnest the conversion of an enormous wing of the Waite Motor Company's plant to the production of that wonderful and delicate mechanism which was to drive America through the air to victory. It began in secrecy and silence. The part of the plant undergoing the change might have vanished from the world, for all the news that issued from it. It was guarded as the vaults of the national Treasury are not guarded, by a little army of government men trained in the arts of vigilance. "But," said the chief of them to Potter, "we can work with a sweet confidence that Germany has her men inside. We've investigated every employee to his birth--we think--but I'll bet my hat more than one spy is planted there.... So we trust nobody.... There are German spies and then there are German spies." Potter looked a question. "Well," said the chief, "there's the ordinary spy that the country's full of. I can catch you one in half an hour if you want him.... And there are the spies who do the real work--and I'd give a year of my life for every one of them I could lay hands on.... The garden variety of spy is a comic-supplement fellow. Tell you how to spot him. Go and stand in a hotel lobby and read a letter. If you feel somebody breathing on the back of your neck, turn around and grab--and you've got your man. It's part of the technique--to breathe on the back of your neck. They're drilled in it like the army is in the goose step. The German is constructed by nature to be obvious. If he's a spy he acts like a spy--as he conceives a spy to be.... There was the fellow we caught trying to blow up a mighty important railroad bridge. Lieutenant in the navy. He disguised himself as a bum; let his beard grow and rubbed grime on his hands. Then he took him his little bomb in a suit-case and went out to do his day's work. Now did he ride to that railroad bridge on a freight, or back in a day coach on a slow train? Not him! He bought a section on the Millionaires' Special--six days' beard and all. Of course we spotted him, and I asked him why the devil he boarded that sort of train in such a get-up. He looked me over supercilious and says, says he: 'I'm a gentleman. You couldn't expect me to ride second class.'" Potter laughed. "They're not all like that, though," he said. "You bet they aren't," said the chief, with compressed lips. "You had some experience, didn't you?" "They tried to blow up the shop," Potter said, briefly. "We've got to act as if we knew they were going to try to blow up _this_ shop.... Your German-Americans in Detroit have been pretty well-behaved." "Yes," said Potter. "There was any quantity of talk before April sixth. I imagine they've quieted down now. Personally I've thought it was just talk and a natural sympathy."