NEW YORK CITY -- On a sweltering Sunday, the sound of hands clapping, arms flapping and voices soaring threatens to lift the roof right off the rafters of the Bethel Gospel Assembly church in Harlem.

Bishop Carlton Brown launches into a sermon on lodgepole pines in Montana that need the heat of forest fires to release their seeds.

"We all need that fire burning inside us to grow," he says, before parishioners queue up for communion.

Hands clasped, Mel Hazel stands stoic as a pine, anchoring a line of fellow deacons. He is dressed impeccably in a coal-black suit, silhouetted by a stained-glass window.

Two pins puncture his lapel. One bears his church's seal. The other, simply 9/11 343, the number of New York firefighters who died on Sept. 11.

Hazel identified victims -- dozens of them his friends -- at the makeshift morgue near ground zero. He had retired earlier that year as a fire marshal after two decades of climbing ladders and the ranks.

"Part of our tradition is not to forget," Hazel says after the service. "Ten years went fast, but it didn't. We lost so many people that day. If there's one thing I learned about this job, it's that the sense of brotherhood transcends race or sex and means everything."

More than 1,500 miles from Minnesota, the search for how Sept. 11 transformed Americans keeps returning to this essential truth. Whether in small towns in Iowa, the Chicago loop or a Harlem church, the stories people recall most vividly a decade later are the ones laced with grace, illuminated with unlikely connections forged between people.

This is what lasts.

Mel Hazel has just such a story. It joins him with Jean and Dan Potter, two 9/11 survivors now living 100 miles from Harlem, in Lord's Valley, Pa. Stepping back with them to that morning a decade ago helps convey the import of what is happening at ground zero now, what the memorial emerging there will mean to tens of thousands of New Yorkers who lived through that day and have carried it with them ever since.

As a kid, Dan had dreamed of becoming a firefighter, ever since a family friend took him to the firehouse where he worked. That day, he met Mel Hazel, then a young firefighter. Hazel mentored Dan through firefighter training, but over the years they lost touch.

In the black smoke and ashy chaos of ground zero, they would meet again.

The memory, Dan says, is "still so vivid I can almost smell it."

A day like any other

Jean Potter threw open the windows of her Battery Park apartment. The World Trade Center sparkled. A storm the night before had scoured the sky, leaving it robin's egg blue with just a whiff of autumn in the air.

Her husband cooked her an asparagus omelette before heading to Staten Island to spend his day off at the fire department, cramming for an upcoming lieutenant's test.

Jean got to work at 7:30 a.m. on the 81st floor of the North Tower. An executive assistant, she wore a lavender pantsuit and lower heels because she planned to be "running around all day."

At 8:46 a.m. "we heard this thunderous explosion," Jean says. "The building started rocking from side to side."

Smoke clogged the air. She found a staircase and started to descend, noticing no one was coming down from the floors above. At the "sky lobby" on Floor 44, she heard another explosion and saw a fireball out of the corner of her eye. The South Tower had been hit.

When she got down to the floors in the 20s, "we started seeing firefighters coming up." She recognized Lt. Vinny Giammona, a well-known prankster and friend of Dan's. It was his 40th birthday and his wife and four daughters were preparing a party.

"He'd show up at the firehouse dressed as Elvis or a cowboy," Dan says, "and if you heard guys laughing, you knew Vinny was here."

The Vinny who Jean encountered in the stairwell was different. "He had a horrible look on his face," she says. "I grabbed his arm and said, 'Vinny, be safe.'"

A desperate search

Someone burst in the door of the classroom where Dan was studying for his test and announced the towers had been attacked. He ran to his pickup and set off to find Jean.

He could see the towers smoking. Speeding over the Verrazano-Narrows Bridge, he eyed the North Tower and figured the plane had crashed below Jean's office on Floor 81. He always told her, in case of fire, head to the roof. He prayed she would be rescued there.

Parking seven blocks away, he ran to the Engine 10-Ladder 10 firehouse to grab his gear. A ghastly scene was unfolding.

"There were body parts in the street. I saw torsos being covered by police and was careful not to step on anything. It looked like a meat locker had exploded overhead."

He threw on his gear next to firefighter Pete Biefeld. They agreed it would be safer to work in tandem. But first, Dan ran back inside the firehouse to grab a forcible-entry tool.

"When I went to catch up to Pete, a guy grabbed me by the door and said, 'Here it comes."'

The South Tower, the second one hit, was twisting, beginning to implode. Biefeld was killed as the 110-story skyscraper collapsed into a seven-story pile of rubble in 12 seconds. Everything turned black. Dan glimpsed a man with a broken leg and a briefcase handcuffed to his wrist. He threw his body over him as debris rained down, then pulled the man into the firehouse.

"You couldn't see or breathe," he says. "I felt like I was swallowing sweat socks, trying not to suffocate."

People began to come out from where they had been hiding, looking "like zombies in a movie, bloody and covered with gray." Dan thought about Jean, who he figured was on the roof of the tower still standing. He needed to get to her.

Then he heard a voice.

"Hey, 31, you OK?"

Beneath the mask of soot, Mel Hazel didn't recognize Dan as his young protégé, but he knew the number on his fire helmet was from his old ladder company.

"Mel, it's me, Dan Potter."

They embraced for an instant.

"I gotta find Jean," Dan said. "Can you help me?"

A police officer sprinted past, hollering that the North Tower was coming down any second. An eerie creaking began. Scrambling under the overhanging ledge of a nearby bank building, Mel and Dan huddled together.

The next 10 seconds, Dan says, "were the fastest slow-motion you ever want to experience."

"It was hell," Hazel says, "like someone stuffed a Brillo pad down your throat. We were in the epicenter. I thought: I'm dead."

They crawled until their heads smacked into something. It was a car.

"Three cars were burning furiously," Dan says. "You can imagine how much light that would let off, but we couldn't see them 2 feet away -- it was so black."

Hazel tried to talk to Dan, but he just walked off.

"He was understandably distraught," Hazel recalls.

Dan slumped against a wall and began to sob. "I said to myself: She's dead."

Eighty-one floors in heels

Jean started screaming at the people in the stairwell. "Move it, move it; we're almost down." Ten more flights to go.

Jet fuel had ignited paper and furniture. Wading through shin-deep water and broken glass in the lobby, Jean was glad she had ignored the people on the way down who told her to remove her heels. She reached the street.

"You're out of the building, thinking you're OK after walking down 81 flights. But then you realize you couldn't outrun the building and we didn't figure it would implode. Which way was it going to fall?"

A cop pulled her into a subway station. She made her way to the Chinatown firehouse. Assuming her husband was safe on Staten Island, not knowing he was frantically searching for her, she started answering phones.

Dan ran home and asked Arturo, his doorman, if he had seen Jean. Arturo shook his head. As he reached his apartment door, Dan could hear the phone ringing. Busting in, he grabbed the phone and heard Jean's aunt hollering over and over: "Is she dead?" He hung up only to hear another ring.

This time it was his father.

"I'm OK, but I can't find Jeannie," Dan said.

"Oh," his father replied, "I know where Jean is."

"Well," Dan responded in classic New York fashion, "you wanna tell me?"

Jean's parents had called Dan's father and told him she was safe in the Chinatown firehouse. About 20 minutes later, Dan walked in and asked whether they had "a beautiful redhead here?"

Someone pointed to a woman covered in gray ash.

Jean didn't expect to see her husband in his firefighting gear, caked with soot, his eyes blood-red from blinking through smoke, ash, tears and tiny glass particles.

As they hugged, she asked, "Where were you?"

Dan responded: "You don't want to know."

Ten years later, Dan and Jean Potter have retired to Lord's Valley, Pa., trying to regain a measure of peace in an idyllic gated community. Memories of that day still jar them.

Mel and his wife invited them over for a barbecue a few years ago. He said a prayer for all the fallen firefighters and they recalled the day Dan and Mel clung to each other as the towers fell.

Multiply their experiences by thousands of New Yorkers. Fleeting, routine things -- a clear, blue sky, a familiar face, some glass on the pavement -- can send them right back to that day. What is materializing at ground zero is intended as a place to let those memories rest.

A reflecting place

A symphony of jackhammers, cranes and beeping trucks rises with the morning sun in lower Manhattan.

The new 104-story One World Trade Center, sheathed in mirrored glass, and a $700 million memorial and museum are being readied to honor those lost.

"This shows that we won't be taken down," says Margaret Power, a carpenter working the site. "This needs to be rebuilt for the families -- and the emotional healing."

Another construction worker, steamfitter Mike Castellano, feels "privileged to work here, but I would have designed it a little different." He grins and sticks out his middle finger. "I would build it like this."

Around the corner, on Liberty Street, Brenda Berkman volunteers as a tour guide. The retired New York Fire Department captain grew up in Richfield and attended St. Olaf College in Northfield. "I don't think any city could have absorbed this like New York," she says.

Once the memorial is finished, Berkman explains, visitors will enter a forest of 400 swamp oak trees. The roar of twin 90-foot waterfalls will drown out the noise of the city. The largest fountains ever made will pour into reflecting pools where the footprints of the twin towers stood. The names of nearly 3,000 victims -- those who died in New York, Washington, D.C., and near Shanksville, Pa. -- are etched around the pools.

"It's going to be pretty spectacular," Berkman says.

At the visitors center, there are film clips, firefighters' equipment and artifacts found in the rubble. Dozens of hand-scrawled posters from the weeks after the attacks beg for miracles and news of lost loved ones. In a quiet room, mementos donated by victims' families -- wedding pictures, letters, golf balls, eyeglasses, karate belts -- hang in a somber floor-to-ceiling collage on three walls.

On the fourth wall, a projector shows the name of each victim. It takes more than four hours to cycle through them all. There's Karen Kincaid, the sister of the pastor in Dubuque, Iowa. There's Vinny Giammona, the firefighter Jean touched on the 20th floor. There's Tim Haviland, the Macalester College graduate who loved looking down on the clouds from his 96th floor office.

"There she is," a father tells his son, pointing to a former co-worker's picture.

"Was she nice, Dad?"

"She was a real nice lady who helped me when I first started at the firm," he says, his hand resting on his son's shoulder. "Her son called her cellphone for weeks afterward, looking for her. It just rang and rang."

Rock-solid friendship

On the 10th anniversary, New York firefighter Karl Van Kasten will make two phone calls, just as he does every year.

The first will be to Jennifer White, whose husband, Teddy, worked in Van Kasten's firehouse and died on 9/11. Their daughter, Taylor, is 12 now. Van Kasten passed the hat around and got $50 from everyone to buy her Disney stock.

The second will be to Pam Glenn, the Minnesota nurse he met in the dark months of recovery efforts, as she delivered food to the crews.

"Pam was one of those typical Americans who came out of the woodwork and were there for us," Van Kasten says. Her generosity so moved him that he split a little chunk of granite he had salvaged from the smoking rubble and sent it to her back in Minnesota. Half is in the little crystal box on Glenn's Inver Grove Heights bedroom bookshelf. The other half is on Van Kasten's living room shelf in Long Island.

"I told her to take this little keepsake from the towers and cherish it," he said, "and tell your grandchildren about it."

This is what lasts.

Curt Brown • 612-673-4767

where America stands a decade later

Read previous installments and view more photos and video at startribune.com/911 or on our new iPad app.

As the 10th anniversary of the Sept. 11, 2001, attacks approaches, reporter Curt Brown and photographer Jerry Holt travel from Minnesota to ground zero, exploring the ways that day altered America.

Sunday: In the Twin Cities, living in a post- 9/11 world.

Monday: Reconciling pride and grief in Iowa.

Tuesday: Fading fears in Chicago, atop the nation's tallest skyscraper.

Wednesday: Into America's most intensely Muslim city, Dearborn, Mich.

Thursday: Near Shanksville, Pa., a return to rural tranquility is elusive.

Today: At ground zero, as a memorial rises, what endures?