Ong said sourly, “Then perhaps we should start with a short presentation by Dr. Melling.”

Susan would have preferred a Q A, to see what Camden would ask. But she had annoyed Ong enough for one session. Obediently she rose.

“Let me start with a brief description of sleep. Researchers have known for a long time that there are actually three kinds of sleep. One is ‘slow-wave sleep,’ characterized on an EEG by delta waves. One is ‘rapid-eye-movement sleep,’ or REM sleep, which is much lighter sleep and contains most dreaming. Together these two make up ‘core sleep.’ The third type of sleep is ‘optional sleep,’ so-called because people seem to get along without it with no ill effects, and some short sleepers don’t do it at all, sleeping naturally only three or four hours a night.”

“That’s me,” Camden said. “I trained myself into it. Couldn’t everybody do that?”

Apparently they were going to have a Q A after all. “No. The actual sleep mechanism has some flexibility, but not the same amount for every person. The raphe nuclei on the brain stem—”

Ong said, “I don’t think we need that level of detail, Susan. Let’s stick to basics.”

Camden said, “The raphe nuclei regulate the balance among neurotransmitters and peptides that leads to a pressure to sleep, don’t they?”

Susan couldn’t help it; she grinned. Camden, the laser-sharp ruthless financier, sat trying to look solemn, a third-grader waiting to have his homework praised. Ong looked sour. Mrs. Camden looked away, out the window.

“Yes, that’s correct, Mr. Camden. You’ve done your research.”

Camden said, “This is my daughter,” and Susan caught her breath. When was the last time she had heard that note of reverence in anyone’s voice? But no one in the room seemed to notice.

“Well, then,” Susan said, “you already know that the reason people sleep is because a pressure to sleep builds up in the brain. Over the past twenty years, research has determined that’s the only reason. Neither slow-wave sleep nor REM sleep serve functions that can’t be carried on while the body and brain are awake. A lot goes on during sleep, but it can go on during wakefulness just as well, if other hormonal adjustments are made.