Jesse quivered and refused to budge.

A creature defined by her keen senses, the yellow Labrador retriever was overwhelmed in an atmosphere stained by the stench of jet fuel and saturated with the growl of heavy machinery and thumping of military helicopters.

But instead of giving up on that hot day in September a decade ago, Jesse and her handler stepped to the side of the Pentagon's north parking lot for a reality check. After a few minutes, the dog got up, approached something in a pile of rubble and gave a distinctive, "Woo, woo, woo."

"I looked," recalled Lisa Nyland, a sergeant with Maryland Natural Resources Police based in Queen Anne's County. "It was a human vertebra."

In the weeks after Sept. 11, 2001, Nyland and Jesse, along with nearly 30 other K-9 teams, worked the site, helping mortuary crews find and identify the remains of the 125 Pentagon employees and 64 people aboard American Airlines Flight 77.

FEMA Urban Search and Rescue teams carried out the initial search of the building, according to the Department of Defense's historical office. But as the mission expanded, it became clear that more dog teams specializing in cadaver work were needed. Handlers on the scene reached out to other handlers, including Nyland.

"It was an honor to be asked," said Nyland. "We all felt that way."

Jesse, a pound pooch from the Caroline County animal shelter, was NRP's first K-9 search dog. By the time of the terrorist attacks, she had compiled a distinguished record of finding children, lost hunters and those killed in boating accidents.

But the Pentagon attack, in which a hijacked jet punched through the west side of the building at 530 mph, almost proved too much for the 7-year-old dog.

"They couldn't train for it any better than humans could," said Nyland. "We were looking for remains, some as small as a fingernail."

Earth-moving machines brought debris to the parking lot, where it was deposited in 30-by-30-foot pads. Each dog searched a square for remains, which were tagged and removed. The material was raked and then inspected by a second K-9 team before it was trucked away.

Dogs and handlers worked 20-minute shifts in the "hot zone" before they were directed to a decontamination tent. Veterinarians bathed thedogs, checked their paws and faces, cleaned their ears and put soothing ointment in their eyes. Handlers were cut out of their hazmat suits and checked. Then the teams would wait for the next rotation.

"It was very stressful. Everything had drywall dust on it. It was hot. Most dogs don't work that many hours," Nyland said. "But you couldn't lose your focus because you didn't want to let anyone down."

At night, Nyland and Jesse were housed in a hotel. Jesse took the king-size bed — the middle of it.

"She stretched out and slept like a rock. I didn't move her," said Nyland.

Although some of the K-9 teams were on loan from police departments, other dogs belonged to volunteer trackers with day jobs, like Heather Roche of Annapolis, founder of Bay Area Rescue Canines.

As Roche backed out of her driveway on Sept. 16, accompanied by her three cadaver dogs, a family acquaintance called out: "Don't find my friend."

"It was so sad. It was part denial, part hope. It wasn't to be," she said. Her acquaintance's friend died in the attack.

Roche had an additional connection: Her father, James Roche, was secretary of the Air Force and in the Pentagon at the time of the attack. Not knowing which side of the building held her father's office, Roche and her mother had to wait until midnight on Sept. 11 to learn he was safe.

For 11 days, Roche combed the site with Alley, 3, her primary search dog; Cassy, at 11 nearing retirement; and 14-month-old Red, who had just been certified.

"It was detailed work, slow and methodical. Sometimes within twisted metal, you'd find human remains," Roche said. "There was so much external stimulation — helicopters flying overhead and the fuel, which permeated everything. It was hard on them.

"There were a lot of times you'd pick something up and put it back down — 'You're wrong, dog.' But a mortuary guy would be right behind you. The dog was right," said Roche. "Nothing looked like what you expected at all."

Despite the hardships, forensic investigators identified 184 of the 189 people who died in the attack. In its official history of the event, the Defense Department credited the dogs with finding many remains and personal effects that would have eluded human search teams.

Alley was tapped for the crew recovery effort after the space shuttle Columbia crashed in 2003. Red went on to work in the aftermath of Hurricane Katrina in 2005.

Jesse helped solve murders and find lost people until slowed by a bad hip and finally lymphoma. The dog was euthanized in 2005, just shy of her 11th birthday. NRP planted a dogwood tree outside the station where Jesse was based. Nyland's only regret is that Jesse never had a badge, as NRP dogs do now.

After working at the Pentagon, Nyland acquired Liberty, born two days after the attack, then Patriot, born on July 4 six years ago. A third dog, Justice, is being trained now.

"I had no intention of getting another dog. But then 9/11 happened," she said. "I told myself, 'If something like this happens again, I've got to be ready.'"

candy.thomson@baltsun.com