"The thing I don't understand," Celtrics said, still leaning on the captain's desk, "is just how do they do it? How did it start, Captain?"

The captain studied Celtrics' face for possible irony; after all, watchbird had been in the papers for months. But then he remembered that Celtrics, like his sidekicks, rarely bothered to turn past the sports pages.

"Well," the captain said, trying to remember what he had read in the Sunday supplements, "these scientists were working on criminology. They were studying murderers, to find out what made them tick. So they found that murderers throw out a different sort of brain wave from ordinary people. And their glands act funny, too. All this happens when they're about to commit a murder. So these scientists worked out a special machine to flash red or something when these brain waves turned on."