 Why are there hidden microphones?
When you try to get a job, they ask to see your ID before they even tell you if there's an opening or not. I've been a garbage man, street-cleaner, ditch-digger—" On the other side of the room, the jukebox came to life with a roar and a group of teen-agers scrambled to the dance floor. There were no longer any prisons—CPA officials had declared loudly and emphatically that their job was to prevent crime, not punish it. It would be hard not to recognize: the room was large, devoid of furniture except for a desk and chairs, but the walls were lined with the controls of television screens, electronic calculators and a hundred other machines that formed New York's mechanical police force.
 The hidden microphones are there to detect criminal activity, so the CPA can stop it before it starts.
 The hidden microphones are there because the girl is an FBI agent, looking to take down a mafia boss.  The hidden microphones are there to make sure the bartender keeps the drinks watered down.  The hidden microphones are there to detect criminal activity, so the CPA can stop it before it starts.  The hidden microphones are there as part of a drug sting.