John Edgewater Smith realized sooner than Benda that he couldn't get out, because, not sticking to work so closely, he had made the attempt sooner. He looked very much worried when Benda next saw him. "What's this? Do you know about it?" he shouted as soon as he had come within hearing distance of Benda. "What's the difference?" Benda replied casually. "Aren't you satisfied?" Smith's face went blank. Benda came close to him, linked arms and led him to a broad vacant lawn in the park. "Listen!" he said softly in Smith's ear. "Don't you suppose these people who lock us in and censor our mail aren't smart enough to spy on what we say to each other?" "Our only hope," Benda continued, "is to learn all we can of what is going on here. Keep your eyes and ears open and meet me here in a week. And now come on; we've been whispering here long enough." * * * * * Oddly enough, the first clue to the puzzle they were trying to solve was supplied by Francisco, New York's former Water Commissioner. Why were they being kept prisoners in the city? There must be more reason for holding them there than the fear that information would be carried out, for none of the three engineers knew anything about the Science Community that could be of any possible consequence to outsiders. They had all stuck rigidly to their own jobs. They met Francisco, very blue and dejected, walking in the park a couple of months later. They had been having weekly meetings, feeling that more frequent rendezvous might excite suspicion. Francisco was overjoyed to see them. "Been trying to figure out why they want us," he said. "There is something deeper than the excuse they have made; that rot about a perfect system and no breaking of rules may be true, but it has nothing to do with us. Now, here are three of us, widely admitted as having good heads on us. We've got to solve this." "The first fact to work on," he continued, "is that there is no real job for me here. This city has no water problem that cannot be worked out by an engineer's office clerk. Why are they holding me here, paying me a profligate salary, for a job that is a joke for a grown-up man? There's something behind it that is not apparent on the surface." The weekly meetings of the three engineers became an established institution. Mindful that their conversation was doubtless the object of attention on the part of the ruling powers of the city through spies and concealed microphones, they were careful to discuss trivial matters most of the time, and mentioned their problem only when alone in the open spaces of the park. * * * * *