In July of last year, one of my oldest college friends, now an unassuming Wall Street financier, treated seven of his closest pals and their families to an all-expenses-paid rafting trip down Idaho's Salmon River. The Middle Fork of the Salmon is 104 miles of snarling, foamy delight, bucketing down 4,000 feet in elevation through more than 100 world-class rapids. It was the trip of a lifetime, in more ways than one.

Leave your wallets locked in the motel safe; you won't need them, promised the pamphlets from Adventure Sun Valley, our river outfitter. Hefty gourmet meals, masseuses in tow and hot showers on shore were part of the experience, but we still bumped up hard against the wild.

Four days in, I was clobbered in the skull and back by boulders careening off a fire-eroded, mudslide-ravaged hillside. I survived, but it's a cautionary tale for those who, like me, consider themselves experienced outdoor adventurers.

The stark beauty of the Middle Fork endures because it bisects one of the largest true wilderness areas in the United States, a place where Congress told federal land managers, "Hands off." That includes "hands off humans." You truly are on your own. It may thunder, burn and flood, and you may well get tossed, tumbled or whacked. Humans are a small component in a vast, ever-changing wilderness.

"The thing you have to keep in mind is it's a very dynamic landscape out there," said U.S. Forest Service district ranger Chris Grove, who oversees the Middle Fork part of the Frank Church-River of No Return Wilderness. That means raw, unmatched recreation, but it also means an ecosystem scoured and sculpted by wildfire, aging forest, climate change, wind and water, with sometimes violent landscape shifts. The storm that felled me created three brand new rapids, miles apart on the river.

Still, fatalities are rare. Once every several years someone drowns or is killed by a falling tree, forest officials said. More common are split lips or twisted ankles. In fact, part of what caught me off guard was that the trip was pretty darn cushy. Despite jaw-dropping whitewater, modern technology makes it possible to sit on your duff in a puffy rubber raft down the entire river, leaving the oars to lean, young guides who work their tails off in exchange for a summer in one of the more beautiful spots in North America.

"Float and Bloat," our guides jokingly dubbed clients who take in the spectacular scenery and amply sized meals.

If you're more adventurous, you'll take the opportunity to fish one of the world's longest natural salmon runs, or paddle your lungs out in a tiny kayak behind the guide boat. More than 10,000 people run the Middle Fork annually, most on packaged trips that launch several times a day through summer. There's no question it's safer than going on your own. It's also far easier to plunk down $900 to $2,000 per person than entering the "non-commercial" lottery, with a 1 in 27 chance of winning a $4-a-day permit.

The Internet is littered with rafting companies, but regulators say they won't play favorites, so there is no rating system. All Idaho river guides must be licensed by the state Outfitters and Guides Licensing Board, with first-aid training and considerable white-water experience. There is a long, unalphabetical listing of licensed outfitters at www.oglb.idaho.gov. Most require life jackets and helmets, and ask you to sign standard liability waiver forms.

My college friend Jim searched online, mailed for brochures and DVDs, then made lengthy phone calls before taking the plunge with Brad Frei's outfit because Frei has a small, Idaho-based owner-operator rather than an out-of-state corporation. On staff, Brad had grandchildren of white-water pioneer Walt Blackadar's, now experienced guides themselves. Above all, he had a full week available with no other customers. It would be just us on the river.

Jim's old roommate Phil, now a Vermont bluegrass fiddler, fretted about the danger. The rest of us lassoed him, his teenage daughter, Aliana, and son, Julian, into coming.

The first three days were a joy. We zipped through Velvet Falls and other iconic rapids. Around every bend was another gorgeous panorama of high altitude conifers, granite slabs and rushing water. There were scorched patches -- wildfires burned 40 miles in 2007. We alternated between lazy floating and bursts of speed paddling. Each evening, our tents were waiting, and we gorged on Dutch oven cooking.

The best part was communing with my old friends in natural hot springs or over imperials of wine that Jim stashed in the supply boat. (An imperial holds the equivalent of eight regular wine bottles.) He and Phil chortled by the campfire exactly as they had done in our Yale dorm years ago. We were happily together again in this middle fork of our lives, with the amazing bonus of watching many of our children now make friends.

On Day 3, after a lunchtime dip in the current, I threw a T-shirt over my bathing suit and climbed aboard the fishing boat with my husband, Frank, and the fly fishing guide. Jim had spared no expense. Frank was in his element, hooking a dozen in an hour. We tarried behind the rest, catching placid spots where a big Chinook might be snoozing.

A humongous thunderstorm crept up on us. Lightning razor-wired overhead. Sideways sheets of rain slapped full bore at the rapids. Our guide wanted to stay on the river, away from toppling trees. My rusty Red Cross training kicked in, and I insisted we get off the water. I was petrified of being electrocuted, shivering in my damp suit until the guide insisted I wear his fleece.

Finally, as Van Morrison would croon, the sun came out, the rain dried up, and we were on our way. We collapsed at camp with hot mugs of tea inside a wonderfully sweltering tent. Later Jim broke out bottles of wine from 1958, the year of our birth, and Phil, Lee and Ted played our favorite "Big Chill"-type tunes.

The next morning the river was muddy with dirt, unleashed from burned side creeks by the previous day's deluge. I was so glad my husband had gotten to fish while it was clear. Still, we paddled happily. Julian, Phil's 10-year-old and the quietest of the kids, proved a master at solo kayaking.

Suddenly our lead guide, young and capable Katherine Blackadar, motioned us urgently off the river. The next rapid we were due to run was submerged under an ominous lake formed by a landslide the night before. A hasty plan was hatched. The guides would take the rafts across the uncharted water, in an effort to dodge submerged hazards. We would portage over the steep bank to safer water below.

Other groups began backing up behind us, and Brad threw down ropes to rappel us faster up the slope. My husband quietly suggested we go back upriver to a more stable point. But Brad was exhorting us upward, and Nancy and Lew's son Robert looked forlorn. I didn't see his parents, so I urged him up the hill. Frank went next, then me.

"Look out!" I heard him shout. BOOM. And then BOOM. I was writhing, staggering.

Voices erupted around me. I heard Lee out on the river.

"What happened?"

"Someone got hit," a strange voice said.

"Who?"

"Someone named Janet," the voice said.

"Janet?" he shrieked, and came running. Brad reached me first, and grabbed my head between his hands, hard.

"You're fine," he shouted, sounding panicked. "It's just like a bad football tackle. I thought that was your brains on the ground," he said, pointing to my sunglasses on the stony slope.

More reassuring were the nurse, nurse practitioner and doctor fortuitously in the rafting group behind us. They gathered around me with professional calm. Marian, also a doctor, arrived breathless.

"This may sound silly, honey, but do you know me?"

"Yes, I know you, Marian," I said wearily.

"OK, don't even know what day it is at this point, but do you know what day it is?" she joked.

"Thursday, I think?" I said, laughing shakily.

I tried to explain that the entire front of my head was numb. They weren't concerned, instead eyeing a patch of moisture below my right nostril and holding quiet discussions out of earshot. A dentist arrived. He explained that a large nerve system across my face and jaw had probably been hit. I would be numb for a while, he predicted, gradually thawing the way anesthesia fades. I was immensely relieved. He took a closer look and began conversing urgently too.

There was a small bone that might have cracked in my skull, Marian said. Although I appeared to be fine, if it was broken, an infection could quickly reach my brain. The liquid under my nostril might be a sign of such a crack. Or it might be an errant teardrop, she assured me. But it would be best to get me out of here for a CAT scan.

Salmon, the nearest town, was 52 miles away over unbroken wilderness. Per federal policy, the forest service does not do evacuations off the Middle Fork. There was a private ranch two hours downstream where a private plane could land. Brad, the outfitter, called tiny Salmon Airport via satellite phone.

I've felt safe around these friends for decades, and this was no exception. I lay cradled in Marian's lap, Frank holding my hand, while Jim, Rudy, Phil, Ted, Lee, Nancy, their spouses and the guides rowed like there was no tomorrow. What could have been a two-hour trip took 45 minutes.

Per those brochures, I had no wallet, no cash, no medical insurance card, no ID. Our spare clothing was in the supply boat far ahead. Jim and Lee had wisely ignored the suggestions, and gave Frank the $300 they had between them. Brad knew the grocery store manager in town, and told us to buy food and clothing on his account. I was flown out on a "beer run" plane, across stomach churning mountain peaks, to a small-town emergency room built to accommodate the likes of me.

My skull was not cracked. I curled up miserably for a few days, but I was OK. The upper part of my face turned black and blue, purple and yellow. I felt as if a giant piece of meat were migrating across my forehead for weeks. I had torn muscles in back, on the side I write with. But as Phil said quietly back on the river, "You're still you, Janet. I can tell."

When Natasha Richardson died in March, I understood just how lucky I was.

So take it from me: If you run the Middle Fork, carry lots of dry clothing in your day bag. Bring cash, ID and your health insurance card, laminated to keep it dry. Don't even think about one of these trips without medical coverage.

And above all, travel with friends. There's no better insurance policy, no matter what life hurls your way. Janet Wilson