"Officer, can you tell me what happened?"

The uniformed man looked up with hurt, bewildered eyes. He said something that the directional mike picked up, but Jerryberry's ears lost it in the crowd noise. He heard it later on the news. "Where's my hat?"

Jerryberry repeated, "What happened here?" while a dozen C.B.A. men around him were interviewing the crowd, and police were pouring out of the displacement booths. The flow of blue uniforms looked like far more than they were. They had to use their shock-sticks to get through the crowd.

Some of the spectators-shoppers-strollers had decided to leave. A wise decision, but impractical. The nearest booths could not be used at all. They held passengers cased in glass, each trying to get his door open against the press of the mob. Every few seconds one would give up and flick out, and another trapped passenger would be pushing at the door.

For blocks around, there was no way to get into a displacement booth. As fast as anyone left a booth, someone else would flick in. Most were nondescript citizens who came to gape. A few carried big cardboard rectangles carelessly printed in fluorescent colors, often with the paint still wet. A different few, nondescript otherwise, had rocks in their pockets.

For Jerryberry, kneeling above the felled policeman and trying to get audible sense out of him, it all seemed to explode. He looked up, and it was a riot.

"It's a riot," he said, awed. The directional mike picked it up.

The crowd surged, and he was moving. He looked back, trying to see if the policeman had gained his feet. If he hadn't, he could be hurt.. but the crowd surged away. In this mob there was no conservation of matter; there were sources and sinks in it, and today all the sinks were sources. The flow had to go somewhere.