The mood at the Dorsey house on a cul-de-sac in Northern Virginia on Sunday was electric, and not only because half of the people there knew what was coming.

The smell of rolls warming in the oven filled the home, and people were packed into the cheery, jewel-toned rooms. A captain from the local fire department was there, along with the mayor. Cameras and photojournalists filled the house. There was even a videographer with a drone, who got an overhead shot as two families finally met because of something Jimmy Dorsey did 30 years ago.

The only thing missing was Jimmy Dorsey.

“He would’ve been extremely nonchalant about it, I think,” his son Aaron Dorsey said. “Maybe he would’ve thought it was too much fuss.”

Sunday was the final installment in the trilogy of Jimmy Dorsey and Mahmoud Ghannoum, the man whose life was forever changed by Dorsey’s one small act of generosity and whose tale was told in this column.

The story began in 1990, when Ghannoum was in Washington for a scientific conference and he was in trouble.

His country, Kuwait, had just been invaded by Saddam Hussein. His city had been obliterated, and his young family was squatting in a dorm room in England. They wanted to come to the United States, and this was Ghannoum’s big shot at finding a job to continue his groundbreaking research on the mycobiome — the fungal community of the human body (the field he named) — and finding a permanent home for his family.

But that weekend was all about the scientists and their presentations. The following week was when the people who do the hiring would be in town. And Ghannoum had just a few dollars left and no way to change the return plane ticket or stay in Washington until the hiring folks arrived.

As he was lamenting his plight, walking the streets of downtown Washington, Ghannoum saw a travel agency and decided he had nothing to lose. Maybe someone would take mercy on him.

The travel agent in charge that day listened to Ghannoum’s story and how one more week could mean everything for him and his family.

He changed the scientist’s ticket. Then he opened his wallet, gave Ghannoum $80 and wished him luck.

It all worked out phenomenally for Ghannoum, who got two job offers that weekend and quickly moved his family to the United States.

Ghannoum is now a professor at Case Western Reserve University, where he’s a world-renowned expert in the rapidly evolving field of gut microbiome science (when you see probiotic stuff at the grocery store, that’s, in part, thanks to Ghannoum’s work), and he has a new book coming out next week.

Ghannoum tried to go back and find that travel agent to thank him and pay him back once his family settled in the United States, but the agency laid off its workers and shut down the next year. He couldn’t remember the agent’s name, only his face and his kind eyes.

So for three decades, Ghannoum told the story of this angel whose small act changed everything for him and his family.

A few months ago, when Ghannoum’s son heard his dad reference the angel (yet again), Afif Ghannoum realized that they actually could find the guy.

So he posted his dad’s story on Facebook with the few details they had — an African American man who worked as a travel agent in downtown Washington in 1990.

I wrote about their search and got scores of tips.

After a ton of phone calls and more searching, after Mahmoud Ghannoum was finally able to see a photo from the 1990s, it became clear that the travel agent was James Dorsey, a veteran of the Vietnam War, a football coach and the first African American firefighter of the Leesburg Volunteer Fire Company.

The joy of that discovery was bittersweet, though.

Dorsey died in February after a long bout with cancer.

The Ghannoum and Dorsey families have been talking for months since they made the connection. Online and over the phone, they’ve been comparing notes and sharing anecdotes.

Aaron Dorsey, Jimmy’s ­33-year-old son, looked back with a new perspective at all the times his dad pulled out some extra cash or bought a meal for a homeless person they’d meet.

“He always told me, ‘Are all your needs met? Do you have food? Are you warm? Do you have clothes? If all of your needs are met, why be selfish? Why not help others who are cold or hungry or homeless?’ ” Aaron said.

The meeting on Sunday was warm hugs, smiles and tears. The home is a gallery of Jimmy Dorsey photos, and his wife, Elaine, gave everyone a tour of his life. The grandkids found common ground in toys and games. And they couldn’t stop marveling at the weirdest coincidence — that the city where Ghannoum eventually settled, Cleveland, is Elaine and Jimmy Dorsey’s hometown.

“We were right down the street from Case Western,” Elaine Dorsey said. “It’s where the, you know, smart kids went.”

And where Ghannoum is now a professor. The university’s film crew was there to document the meeting.

Ghannoum held Elaine Dorsey’s hand as the two families gathered around them in the kitchen.

“I’m really grateful to meet Elaine and the Dorsey family,” Ghannoum said. “And I’m thankful to God and all the things that made this happen.”

Ghannoum also unveiled his big surprise to the Dorsey family, explained on a brass plaque he gave to Elaine, to join the mayor’s proclamation already on their wall.

“Jimmy Dorsey touched the lives of so many people in ways he will never know,” the plaque said. “The James R. ‘Jimmy’ Dorsey Memorial Scholarship was established to perpetuate Jimmy’s virtues and endearing qualities. His generosity and kindness will never be forgotten.”

Ghannoum established the fund with $25,000 seed money, university officials said. He told me he will keep adding money to grow the fund.

“It’s for someone like me, who needs a little help,” Ghannoum said.

And it’s for someone who will promise to understand the outsize impact that a life of kindness and generosity — the life Jimmy Dorsey quietly led — can have on generations of people.

Twitter: @petulad

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