A STRANGE SOUND from the baby monitor woke me out of deep sleep. I lay in bed for a moment, my thoughts flapping through the darkness like terrified bats. The monitor croaked again. Then came a weird gurgling sound, similar to the one my little sister made once when she inhaled a sliver of cantaloupe. I got up, stumbled around the room looking for a robe, and ran downstairs.

Doc lay on his back, eyes wide open but unfocused, fists grabbing the bed sheet. The gurgles were his attempts to breathe. Sweat pasted a tuft of white hair to his forehead. I spoke his name--no response. I touched his hand--no reaction. He's dying, I thought. What do I do? He'd strictly instructed my wife and me not to intervene medically when his time came. In fact, every day for months he'd talked about wanting to die. Now it seemed Doc's wish was coming true. My wife wasn't home, and Doc's two sons were two thousand miles away. My 93-year-old friend was dying, and I was alone with him.

What do you say to someone at the moment of his death? I didn't know--I'd never seen anyone die before. I wanted to comfort him, tell him something to make his trip easier, assure him that he was loved. But all I could think to say was, "Doc, I'm here with you. I'm here. It's OK. I'm here. I'm here. I'm here."

I repeated these words like a mantra, afraid to touch him again, watching as his 100-pound body curved into an unlikely arc, every muscle rigid. The smell of urine rose from the bed. Doc's face gradually turned pomegranate red. He wasn't gurgling anymore, but instead made an unearthly whistling sound through clenched teeth. Then his body sank back into the bed. Silence. At some point he'd closed his eyes. I was aware of my arteries pounding in my neck, and his arteries doing absolutely nothing.

My wife and I had lived with Doc for six years. At first, our arrangement was to prepare dinner and provide him with occasional company, in exchange for room and board in his 18-room, four-story house in Madison, Wisconsin. Doc had filled the house with plants, books, and antique furniture, and he tended a huge garden with dozens of varieties of flowering plants and five different kinds of grapes. Living rent-free in that house was an incredible deal for two graduate students, a deal made sweeter when Doc quickly became a friend, mentor, and grandfather figure.

At age 90, Doc still drove to his university office every day, one of those guys who poked along at 15 miles per hour, only the top of his hat visible over the steering wheel. His name was Harland Mossman, and he was a retired medical school professor, the world's top authority on the comparative anatomy of vertebrate fetal membranes. He made his daily trip to campus to tend his vast collection of pickled placentas.

Doc loved research, had thrived in his lifetime of academia, and couldn't understand my bouts with depression. He'd ask me, "How can you be depressed, when there's so much work to be done? Just do the work." I couldn't tell him that the work was the problem.

While Doc reveled in analyzing placentas until he understood every anatomical detail, I specialized in starting and abandoning research projects. I'd charge into a new study with Doc-like enthusiasm, but after a few months I'd feel the inevitable ice cube of boredom in my brain.

First I studied meteorology, cooped up in a sealed building, running endless computer simulations of a European storm. I longed to be outside under the real sky, not trapped inside manipulating digital clouds. So I transferred into the Limnology Department to study lakes. My job was to net fish for a food web study. I saw plenty of real clouds, and got paid to squeeze fish on lakes throughout Wisconsin. This should have been the perfect research project. I should have been happy, I thought, so I tried to ignore the chill growing inside my head. I didn't want to disappoint Doc, so I never told him that research left me empty.

After we had lived with Doc for about five years, his health started to fail. I allowed myself to become enveloped in caring for him. I did it willingly. He was my friend, and it gave me an excuse to avoid my research. Instead of making the hard decision to drop out of grad school, I opted for the "easy" choice of letting my caregiver role expand and my student role contract. I still tried to work on my Ph.D. dissertation, but my thoughts turned increasingly to my ailing white-haired buddy. But now Doc was dead.

Or was he? I thought I saw twitches in his neck. Could it be possible? Yes, he definitely had a pulse--his blood was starting to move. Then his chest started to rise and fall. In a few minutes, he opened his eyes, sat up, and said, "I'd like some apple juice."

I learned later that Doc's convincing "death" was something called a Stokes-Adams attack. His heart's natural pacemaker had stopped issuing signals. Doc's heart stopped beating, but his lungs tried to keep going, causing the gurgling sounds that woke me up. When his lungs quit, Doc's blood darkened from lack of oxygen, making his face flush. These sequential bodily failures mark the usual downward spiral into death after the heart stops.

But Doc's heart wasn't done. A secondary pacemaker, a natural backup system, kicked in. Doc returned to his body. He didn't remember his trip out to the ultimate threshold, or at least he never told me about it. He said he couldn't remember anything. Doc and I lived through four more false deaths that night. He established a world record for resurrections in a 12-hour period.

Doc lived a few more months, but the living was punctuated by dozens of little deaths, as Stokes-Adams attacks recurred at unpredictable intervals. I spent hours by his bed, which was rolled up against a window so that he could watch the birds outside in his garden. We talked about all the important stuff: politics, religion, our families, and trout fishing. I tried to appear interested when he'd launch into impassioned monologues about placentas: "If taxonomists would just examine the evidence from the placenta, they'd see that lemurs are actually tree-climbing horses!"

As winter deepened, Doc became less interested in living. His silences lengthened, and he stopped watching the birds. Sometimes he'd look at me with terror in his eyes and ask, "Who are you, and what are you doing in my house?" Finally, at six o'clock on a December morning, he had another Stokes-Adams attack, his backup pacemaker failed him, and he died.

Sometimes revelations are anything but sudden. Sometimes they come on like the gradual greening of California hillsides in early spring. It was many months after Doc's death before I stopped having nightly dreams in which he was somehow alive again and needed me to take care of him. But in those same months I felt a rising certainty that I needed to change my life path, and finally I did. I dropped out of graduate school--and felt my internal clouds start to melt away.

I'm a science writer now. It's a career where I can learn about science--any discipline that interests me--and I don't have to do the research. I finally found work that I can revel in. I think Doc would have approved. He also liked to roam through the diverse landscapes of science.

Doc's death provided me with another revelation: I, too, am going to die. I had always known this, of course. But watching life slip from Doc's body brought the realization home like a hard punch to the gut. At the same time, his death reinforced the awareness that I am alive, right now.

Doc's biggest gift to me was the realization that I, too, am here in the world. I'm here.