IN ONE WEEK the trees had surrendered their colors, the nighttime temperatures had plummeted, and the rivers were shutting down. The taimen vanished from knowledge then. Local lore held that they migrated up the Eg to Lake Hovsgol, or downstream to Lake Baikal, but the scientists' partial evidence indicated that they probably stayed right where they were.

I willed myself to believe that the earth would spin, the river would flow. The aircraft would come. And on Sunday, with one finger left on my calendar, I fished.

Charlie had seen, once, a big taimen resting in a deep bend of the river. We drifted quietly down into it and he pointed out where an old landslide had poured down a bank into the water. "That's where you're gonna catch him," he said.

On the last day of the last week of the brief fishing season on the last river full of taimen, I made one last cast. I dragged an immense black popper across the current, and the hit was so big that I thought Jim had thrown a bowling ball into the water. I hooked, played, and then, after 20 seconds, lost the fish. The mouths of taimen are hard as metal plates, and they throw off a lot of hooks.

The foam fly bobbed to the surface as the blood ran out of my face. Charlie had said a hundred times that taimen will come back around and hit a fly again. Paralyzed, I let the fly ride there, every ounce of attention coiled into my hands, but nothing happened.

Yet luck is made. Second chances are made. I lifted the fly, arced a single false cast, and dropped it back over by the landslide. Nothing. In despair I pulled it in toward the boat, slowly, the way Charlie had taught me. This time the taimen hit with a whitewater splash full of teeth, dived back down with a flash of dark tail, and then the fly and the fish came tight on the line, thrashing.

By the time I wrestled it in, my arm was trembling with lactic exhaustion. Taimen are not spectacular fighters, but their size and weight make it a brutal contest. "Thirty-seven inches," Charlie said, looking up from the net. Almost a meter long. This wasn't Anna Nicole, but the fish was fat enough to melt over my fingers like Monterey Jack in a microwave. Holding the sleek gray beast out of the water, posing for photographs, I accumulated some seriously bad karma.

Before releasing it, we studied a deep, round scar in its back. The fish appeared to have survived a stabbing by poachers, who use long wooden tridents. I revived it until my fingers were numbed by the Uur, and the taimen abruptly kicked its way free.

Five minutes later we saw the fish one last time. It was finning slowly against the sandy bottom, down in the black heart of the river. Tired, but still alive. A survivor.

I TOOK JIM'S ADVICE and peed before getting into the helicopter, and the magic carpet had us in Ulan Bator by lunch. A veteran of many goodbyes, Jim simply handed me his old copies of Time and caught a flight to Beijing. Then Central Asia kicked in: A sudden windstorm shut down the airport, stranding me in the capital, amid broken sidewalks and construction cranes, for more than a day.

The phrase "My wife is in the hospital" can melt the coldest hearts, and once I reached South Korea I was allowed to simply walk onto the next direct flight to New York. We burned up and over the glacial reaches of Alaska, nicked the Arctic Circle at 33,000 feet, and finally, 14 hours later, dropped into New York, bathed in solar radiation and unwatchable movies the whole way.

From there, everything went terribly, shockingly right. I stumbled into the hospital just as my wife was signing the consent form for anesthesia. When I dropped all my fishing gear, a cloud of Mongolian dust rose into the sparkling room.

The surgery was far worse in anticipation than in the actual event. Twenty brief minutes and a clean bill of health, with walking papers that afternoon. That night we lay in bed, exhausted, infinitely relieved, listening to the elevated train rumble past our brick house and to the vain wailings of car alarms down by the Gowanus Canal.

So that is one last reason to go to Mongolia, to go such a terrible distance away. You have to learn that paradise is not a silver creature in a black stream lined with pine trees. I'd found my good place. Nothing could touch us here.