Gray and black mud coats everything. The mud is 70 feet deep in places, shot through with huge shattered evergreens, splintered houses and outbuildings, twisted cars-pushed together by the force of the slide. A river has backed up and flooded parts of that mile-square pile. Scattered somewhere beneath it are the still missing and dead. And it keeps raining.

The search continues in that purgatory, created almost two weeks ago when part of a mountain sheared off and roared to the bottom of a river valley in Oso, Washington. It will probably go on for weeks.

Cadaver dogs, also called human remains detection dogs, are at the epicenter of that search. Labradors, German shepherds, golden retrievers, even a Weimeraner, ghost-like yet still vibrantly colored against that glacial mud, scramble to balance on logs, pick their way over the rubble of crushed houses. All the time, they use their noses to detect the complex odor of human death.

The dogs, handlers alongside them, have to work slowly and methodically. Moving itself is a challenge, even for a canine with four legs and agility training. Their human handlers are clumsier. Crawling over huge logs. Avoiding twisted metal. Pulling boots out of mud the consistency of freshly poured concrete. Sometimes leaving a boot behind, where a helpful firefighter rescues it and helps get it back on the handler's foot. Clearing a dog's nostrils when she takes too deep a snort into the mud. Making sure the dog doesn't end up slipping off floating debris or logs and get stuck underneath. Helping a dog slide down into and out of ponds created by the incessant rain and the flooding river. Checking, checking, checking for scent.

I was listening to dog handlers describe that terrible scene from nearly 3,000 miles away in North Carolina, wishing that I still lived in the Northwest where I grew up. Wishing I was there, at the scene. Wishing that my 10-year-old cadaver dog, Solo, was much younger, or that my agile, driven, but still juvenile cadaver dog in training, Coda, was older. They are bookends, each at one spectrum of a dog's life. It's not that any cadaver dog handler wishes for a disaster. To the contrary. But if there is a disaster, you want to be there, working with your dog.

Everyone at the Oso site knows no victims remain alive. But the search hasn't stopped. It has shifted. The number of confirmed dead stands at 30; the number of missing at 15. Cadaver dogs, both handlers and officials say, have been crucial in helping both to pinpoint victims' locations and to narrow areas to search. Everyone knows it might not be possible to recover and identify all the victims. But dogs, handlers and searchers are all part of a team that is steadily lowering the number of the missing, one muddy step at a time.

The earlier euphemism that media and officials used for the search at Oso, "specially trained dogs," has been abandoned. These dogs, cadaver dogs, are trained to search for the scent of human remains. As tragic as this disaster is, the dogs still provide hope. It's crucial work to recover the dead-and the dogs with their handlers are the first step.

"Every area we went to, I was told, ‘Dog teams are our main resource, our guides,'" said Cat Best, of Walla Walla Sheriff SAR K9, who worked the area with her black German shepherd, Izzy. It was the first disaster she had worked, and she was honored and awed to be there.

Said another handler, Phoebe Duke of Intermountain Search Dogs out of Spokane, Wash., who worked with her nearly 9-year-old golden retriever, Porter, for three days at Oso and has turned around to return after a rest: "The search is totally around the dogs."

Their dogs were willing to go in, to go up, to go over. They are trained to recognize the complex scent of human remains, with its hundreds of volatile compounds, and to signal that find to their handlers. Scent may be wafting from under water, running down the current, getting pulled into the debris of log piles, or slipping out from under many feet of mud, perhaps because a piece of debris has given it enough air to escape. It's a confused scent picture on the site.

Nonetheless, for the dogs working to detect the scent of human remains, it isn't traumatic. It's a smell associated with a game, with a reward, with play. They love it. Dogs associate their particular job-finding the dead-with positive things, not with tragedy.

Handlers and their flankers mark spots where a dog has expressed interest or alerted, and then move on. Sometimes, they'll bring in another dog to see if they can narrow the area. Searchers can come in with shovels and hands, and sometimes a backhoe to get underneath. And if someone is found, or if part of someone is found, they are removed carefully. But the search at that spot doesn't necessarily end there. No one can assume, if another dog returns to that site and expresses interest, that they might not have to dig another six feet further down and find someone else, or something else. The dog may have still found residual scent from the person already removed. But perhaps not. It is an excavation of heartbreak and infinite guesswork.

On a disaster scene like this, just as in all difficult work, it's never about one thing. It's a team effort, and there is no perfect tool. Experienced handlers know that dogs can't provide all the answers. They aren't magic. And sometimes, even when a dog alerts, effectively telling the handler "I smell something here," the handler might not learn the answer, amid the chaos and challenges of the site.

"It can be very frustrating," said Marcia Koenig, of King County Search Dogs. "You may never know." Marcia, with more than 40 years of search-dog handling experience, worked the Oso landslide for several days, up to her knees in mud, with her 7-year-old sable shepherd, Raven, working out in front and alongside.

Even experienced dogs and their human handlers are pushed to their physical limits at Oso. They can become exhausted in what is a horrendous search environment. The mud and water is bone-chilling. What's astonishing is that there have been so few injuries, except for a couple of scrapes and cut pads, and one case of hypothermia. But dogs can't do it all. Mud, water, sand, and debris can change where scent is, or block access to it entirely. And in a disaster of this magnitude, sometimes the trained response handlers are accustomed to seeing, such as a dog lying down or barking, isn't there. Handlers have to know their dogs' body language, to watch to see if they are interested, or "in odor."

Somehow, through all of this, the dogs are communicating their knowledge to their handlers. They are accessing places that aren't safe for people. They are working off lead, directed by commands and signals to places their human handlers can't access. The dogs' noses are giving searchers places to focus their attentions. And in numerous instances, people who have worked at Oso say, the dogs are the first step in returning the dead to their families and friends.

"The dogs are working their hearts out," Marcia Koenig said.

Marcia Koenig is no stranger to working in disasters. She and her prior search dog, Coyote, were flown to Guam in 1997 when Korean Flight 801 crashed and tore a ragged hole down the mountainside. She worked after Hurricane Katrina in 2005. She's the kind of person you want to work with: cheerful, enthusiastic, happy to see other handlers and their dogs succeed. She and her husband, Andy Rebmann, who wrote the book on handling cadaver dogs, have trained people and dogs across the world how to look for the dead. That book, The Cadaver Dog Handbook, was my bible when I started learning how to train Solo as a cadaver dog in 2004. Andy was on the site at Oso as well, to help coordinate some of the efforts, and to use his German shepherd, Carlo, on a water search.

But even with more than four decades of search experience, Marcia is finding Oso is presenting new challenges to her, to other experienced handlers, and to their dogs.

Oso also is showing handlers new sides to their dogs. Raven is usually standoffish. Andy calls her "the princess." But at Oso, she stepped down from her throne. "Normally she has no interest in strangers and just turns away from them," Marcia said. "But at the search site every time someone wants to pet her, she snuggles up to them, licks them and tries to get in their lap if they're sitting down."

Cat Best, who had never deployed on a disaster, although she had been on a number of searches, watched the hundreds of hours of training Izzy pay off, and was enormously grateful for that feeling of becoming one with the dog: "The directions we had practiced so many times-forward, back, left, right, hup, over and this way-became imperative for survival and an ongoing conversation between us. We navigated logs across quicksand, me in my human form just trying not to fall, Izzy with strong dexterity, like she had done it a million times."

In the meantime, dogs worked scent. That was what happened all over what handlers call "the pile." Searchers and handlers have to take the dog's interest, use the science and knowledge about scent, and figure out where to go next. Scent moves. Think about a colored smoke bomb and what it does in wind and in rain, and you start to get the picture. Often, a dog's alert is just the beginning of a complex evacuation, using backhoe, shovels, and sometimes bare hands.

In the meantime, some dogs who have worked several days, are getting a well-deserved break. More than 30 dogs have been on the site. More are being brought in from other states to give the dogs who have worked for days a rest.

But the rest won't last long. While the old adage, "train hard, search easy" couldn't be applied in this case, facing mountains of mud and debris, that doesn't mean handlers and trainers aren't already mulling over how to incorporate the lessons they learned on the site to future trainings.

Although I only had photographs and word pictures in my head, although I am on the opposite coast from Washington, I started thinking about what I could do to incorporate lessons from this disaster. How I might train my little 20-month-old minx, Coda, to best prepare her, and me, for such a terrible search. It was almost beyond imagining. Almost.

Driving home to Spokane after several days of searching, Phoebe Duke and her fellow team members were already jotting notes on how they could make sure their dogs were even better prepared. Making sure all the dogs were used to getting on ATVs. Getting them accustomed to helicopter blade backwash. Training them so they could balance easily on log piles, even when those logs shifted under their feet.

And Marcia Koenig, though she admits that she is covered with bruises and exhausted, said she was going out in the morning with Andy. To work with their dogs on training problems. To make sure the dogs were happy and successful. And ready for the next search.