"Remember the opossum?" I ask.

"Oh yes," my father answers. He makes an opossum expression. The ghost-faced animal had lurched its way into our tent. Coolly and gently, my father had rapped it on the nose. Now he is driving with the same coolness, a father's certainty about major operations, except his eyes are pink again.

"Are you sleepy?" I ask. Even at 8, I understand the trickiness of certain questions.

"Nope," he says, and adjusts the vent.

"Sure?" I ask.

We drive, still fast. Washington's another hour. I am reluctantly tucking into sleep position when my father's head drops. We swerve hard, the world in the windshield pitching right at a nauseating angle. Horns scream as I grab the wheel. I yank us away from the median rail and wonder if we'll turn over. My father's head jerks up now and his hands shoot to the wheel.

"Thanks, I got it now," he says.

Narcolepsy -- the neurological disorder that sends people into frequent and sudden sleeps -- follows a familiar path, I learn years later: Everyone's heard of it, no one understands it. Even sleep researchers shrug, helpless to find a cause or a cure. They know this: Narcolepsy's primary symptom, excessive daytime sleepiness (EDS), is virtually irresistible. EDS steals people away mid-sentence, mid-step.

The disorder is marked by an onset of REM sleep almost immediately after sleep begins, rather than the standard 90 minutes later. Perhaps as a result of this REM disturbance -- even here researchers must speculate -- the narcoleptic often experiences intense, nightmarish hallucinations upon losing consciousness. Another common symptom of the disorder is cataplexy, in which strong emotion -- laughter, anger, surprise, anticipation -- triggers a sudden episode of muscle weakness. Patients describe laughing fits that leave them conscious but rag-doll limp for several minutes.

Experts can't decide precisely how narcoleptics contract the disorder; it is hereditary to some extent, but also somewhat environmental. Whereas a child can be born with a genetic predisposition to the disorder, the narcolepsy can remain dormant until activated by such triggers as illness, stress, drug usage, viral and bacterial agents, abrupt changes in sleep-wake cycles or even hormonal changes. In one study, researchers located a gene called HLA-DR2 and/or HLA DQwl in 98 percent of people with narcolepsy -- but one quarter of people without the condition also had one of the same genes. The mystery means no cure. Doctors sometimes prescribe amphetamines to rev up the narcoleptic's mental alertness, but this strategy doesn't approach the roots of the disorder.

Most researchers figure one person in 2000 suffers from some degree of narcolepsy -- just below the incidence of multiple sclerosis -- although the American Narcolepsy Association says it's more like one in 500. At the heart of the discrepancy lies the disorder's double heartbreak: For all the reasons people don't get medical information -- poor dissemination, a lack of educational funding, incomplete research -- well over half of all narcolepsy sufferers are said to suffer in the dark. EDS, after all, looks like nothing more than tiredness to the untrained eye.

Dismissed as lazy, many undiagnosed narcoleptics move through their lives in a sleepy cloud of shame. Of the few studies evaluating the disorder's psychosocial consequences, one claims them to be more devastating than those of epilepsy.

Next page | The mystery of the Other World stuffed into a dozen sudden naps