It was nearly dark when our neighbor pulled into our driveway with a brace-yourself look in his eye. “He’s in rough shape,” he warned, as he got out of his pickup and walked back to open the trailer. “Rougher than I thought.”

I took a look at the donkey huddled inside, then grabbed my phone to call for backup.

“Scott, you’ve got to get over here. This is really bad.”

“Right away,” Scott replied. “And don’t worry. I’ve seen it all.”

My neighbor tried to lead the donkey out of the trailer but it could barely walk. Its fur was crusted with dung, turning its white belly black. In places the fur had torn away, revealing raw skin almost certainly infested with parasites. He was barrel-shaped and bloated from poor feed and his mouth was a mess, with one tooth so rotten it fell right out when touched. Worst of all were his hooves, so monstrously overgrown they looked like swim fins. The donkey managed the few shuffling steps to the bottom of the ramp and then stopped, head hanging.

When Scott arrived, I was reassured by his confident grin — until it faded. “I’ve seen it all,” Scott repeated. “But not this.”

By day, Scott is a sales rep for a rural Pennsylvania company that makes those clogs that chefs and dancers love. In the evenings, he shifts his focus from feet to hooves, his real passion. Scott grew up in upstate New York and paid his way through college by learning to fit horses for shoes. After he moved to our neighborhood in Lancaster County, Pa. — home of one of America’s largest Amish communities — he became the go-to guy whenever local farmers needed help with their big work mules and buggy horses.

Some weekends, Scott and his wife, Tanya, would wander around horse auctions as unofficial animal advocates, speaking up when they spotted a horse that needed care. Once, Tanya jumped in front of an auction trailer headed to the slaughterhouse, pulled out her wallet, and offered the driver any price for a mini donkey she’d spotted in the back. The little donkey was so far gone that the driver gave it to her free. Tanya thought she could heal it, and she was right. Today, tiny Matilda trots along when she and Scott take their carriage horses out for a drive.

But this gray donkey that turned up in my driveway was even worse off than Matilda. “How did this happen?” Scott asked.

“Hoarder,” I explained. My Mennonite neighbor had stepped in after discovering a church member was keeping a donkey and goats penned in squalor in a cramped shed. The goats were easy to place — someone in Lancaster can always use a free lawn mower — but donkeys are tough. They’re famously ornery, known for biting and kicking, and serve no purpose on a working farm. They can’t be milked or butchered or, in many cases, even ridden. Keeping them in hay and feed can be expensive, and that’s before you’re shelling out for dental care and deworming and vaccinations.

So why did I want him?

I didn’t. Not at that moment, that’s for sure. We’d agreed to take him in only because we figured he’d be fun and trouble-free. We had moved from Philadelphia to a small farm in southern Lancaster County a few years ago, and as transplanted city folk who knew nothing about animals, we’d gotten a kick out of raising a few sheep and chickens. We’d wanted to help a creature in need, but this kind of creature — and this kind of need — was way beyond anything I’d imagined.

“The most humane thing might be to put him down now,” Scott said. The hooves, he explained, were a death sentence. Donkeys usually keep their hooves naturally pumiced by foraging for long miles over rocky ground. But if you pen them up on soggy straw, or even leave them standing around all the time in a grassy meadow, their hooves will eventually curl and become deformed. The damage can be irreversible and worse, a hobbled equine can’t digest its food, leading to an excruciating death.

Scott paused to think for a moment. “Do you have a hacksaw?”

I fetched one from the shed, then held the donkey’s legs as Scott sawed the hooves until they were short enough to be clipped and rasped down with a file. “I don’t know if this will work,” Scott said. “If he’s not walking by tomorrow, all we can do is make him comfortable before he goes.”

Comfort was his wife’s department, and it wasn’t long before Tanya was roaring up the driveway in her pickup truck. Tanya is a licensed veterinary technician with more than 30 years of experience as a horse trainer. She charged into action with her medical kitand shears, swiveling her head back and forth as she alternately crooned to the donkey and barked commands back at me.

“Good donkey!” she purred. “Good — ” She paused. “What’s his name?”

“Um… Sherman?” We’d just seen “Saving Mr. Banks” and my kids had gotten a kick out of the songwriting Sherman brothers.

“Good Sherman!” Tanya said. Her clippers growled through Sherman’s matted belly fur as she rattled off a list of things for me to fetch from the house: baby shampoo, curry comb, a hose. “You need to lather him from nose to tail!” she commanded, before suddenly clicking off her shears.

“Now, look,” Tanya said. “If he makes it, you can’t just stick a ribbon on his tail and leave him standing in a field like Eeyore. He’s been abused and abandoned, and that can make an animal crazy with despair. You need to give this animal a purpose. You need to find him a job.”

Secretly, I already had something in mind. It was too ridiculous to say out loud, not unless I wanted to reveal I knew nothing about donkeys and probably shouldn’t have one. It popped into my head as soon as Tanya began assessing the grim wreckage of Sherman’s body, and maybe that’s why I kept circling back to it: Focusing on a glorious long shot was a lot more pleasant than the ugly reality that was kicking us in the face.

So while Sherman was struggling to walk, I was imagining that he could run.

After all, it had worked for me. A few years earlier, I’d been a broken-down ex-athlete battling constant injuries and 50 excess pounds. I hated the monotony of the gym, and the endless yawning miles of cycling. I kind of liked running, but every time I got some momentum, I got hurt. “No surprise,” doctors kept telling me. “Running is terrible for the body, especially big ones like yours.”

For years I believed them — until, in 2006, I found myself in a bizarre adventure at the bottom of a Mexican canyon, where I learned the lost secrets of the world’s greatest ultrarunners: the Tarahumara Indians. I shared those discoveries in my book, “Born to Run,” which became a sensation because so many other people were struggling with the same challenges. Since then, I’ve run thousands of miles in bare feet or the thinnest of sandals, and become convinced that we evolved to fly across the landscape on our own two springy, remarkably durable legs. Movement is our best medicine — so wouldn’t that also be true for Sherman, with the blood of wild African asses in his veins?

I knew just the thing — maybe. While researching “Born to Run,” I’d stumbled across a ragtag crew in the Rocky Mountains who kept alive an old miners’ tradition of running alongside donkeys in races as long as 30 miles. Was it possible? Could I bring Sherman back from this calamity so that he and I, side by side, could run an ultramarathon?

Secretly, I loved the idea of exploring another lost skill the way I had with barefoot running. Animal alliances were once our great art; for most of human existence we relied on other creatures. We could persuade horses and elephants to carry us into battle, and hawks to kill rabbits and drop them at our feet. We could saddle reindeer and herd geese and yoke yaks. Dogs would leap to us at a whistle and throw their bodies in front of anyone who meant us harm. Animals were our companions and transportation, our security systems and wilderness guides. It was a skill all of us shared because animals were all around us. Only recently have we severed that connection and now, with the surge in interest in therapy dogs, celebrity pet trainers, and equine treatment for everything from Parkinson’s disease to sex addiction to post-traumatic stress disorder, we’re trying to recover what we’ve lost.

Running with Sherman would take that challenge to the next level. It would mean forging a bond with a member of one of the most notoriously stubborn species on earth and training for big miles in nasty weather. But first, we had to keep him alive.