Marc O’Brien was panicking.

Like millions across the country, he was in charge of preparing a Thanksgiving meal. But instead of a family or party, he stood to disappoint 400 men — many of them ravenous, some who had not eaten in days. At the Central Union Mission homeless shelter in downtown D.C., this was the most important meal of the year.

O’Brien, 62, checked his watch: 11:40 a.m., just 20 minutes to the first meal service. He scuttled into the kitchen, making mental notes. There were 14 volunteers missing.

“Are you a volunteer?” he yelled, eyeing a middle-aged woman who had just walked into the Mission’s cafeteria. “Come in, come in, hurry please, apron on.”

Staff members and volunteers at the Central Union Mission, the oldest private social service agency in D.C., spend months preparing for this meal. In the days preceding, they coordinate donations to provide food — including several hundred turkeys — to 4,000 people in need. And on the day of, they serve traditional Thanksgiving meals at lunch and dinner to anyone who walks through their doors. Staff try to make the day special, said Mission President Joe Mettimano, though for many who end up at the Mission, the meal is often bittersweet.

This year, the shelter will serve about 450 people on Thanksgiving Day. It is among the highest in recent years, and “a miracle,” given the recent regionwide dip in charitable giving, Mettimano said. But in a city where more than 6,500 people do not have permanent shelter, it is still not enough.

D.C. has one of the highest rates of homelessness in the country. According to a recent count, the number of homeless families in the District dropped 15 percent compared to last year, but the number of homeless, single adults increased by 2.8 percent.

Across the city this week, various groups have stepped up to help, offering holiday meals to the homeless and others in need. Franklin Square was a patchwork of friendly charitable competition Thursday as a handful of organizations set up stations on the thinning autumn grass and dispensed food, clothes and toiletries.

Among the volunteers were Jonathan and Thomas Bangura, 13-year-old cousins from Fredericksburg, Va., who shivered as they passed out water while wearing thin blue latex gloves.

“I used to think Thanksgiving was just about having a feast with your family,” Jonathan said, handing a bottle to a man in a wheelchair. “But now I know it’s about helping others and sharing happiness.”

At Central Union Mission, Sylvester Morgan and Alven Walken, both 62 and residents of the men’s shelter, were among the first served their plates of Thanksgiving food on Thursday afternoon.

“Most people eat their Thanksgiving at 5 o’clock,” Walken said to his friend.

“Well, there’s gonna be another at 6,” Morgan replied, his eyes focused on the mashed potatoes.

“Uh-huh. You bet I’m gonna be back.”

Morgan and Walken cleaned out their plates in minutes. Chuckling, they waved down a volunteer to ask for soda.

Residents at the shelter usually line up to get their food from a counter, but for Thanksgiving the men were served by volunteers in white aprons and hairnets. The idea, said chef Monique Woodland, was for the cafeteria to feel as much like a restaurant as possible. The typically spartan room was decorated with helium balloons and sparkling streamers. Christmas music played from a speaker.

Richard Bell, 53, said he appreciates the effort that staff puts into the event but hopes that after two years at the shelter, this will be his last Thanksgiving here.

After losing his job in 2011, Bell fell into alcoholism and stopped being able to afford his rental apartment in Charles County, Md. His wife and daughter moved in with other family, and Bell moved into a hotel, where he attempted suicide.

One hospital stay and two shelters later, Bell feels close to getting his life back on track, he said Thursday. Next year, he wants to have his own home again in the Maryland suburbs and to cook a Thanksgiving meal for his family just like he used to. He wants to prepare a turkey while listening to his wife and daughter watch Christmas movies on Lifetime.

“That’s what I miss,” Bell said. “That’s what I miss the most.”

Maurice Hunter, 53, also misses the smell of the kitchen.

The former waiter has stayed at the Mission for nearly a year, but said he hopes to move out by next summer.

Thanksgiving has always brought back fraught memories, Hunter said. As a kid, it was his favorite time of the year. But after his parents divorced when he was 9, things changed: His parents found new partners, and at 14, he was kicked out of his family home. Most years since, he has spent Thanksgiving alone.

In 2017, when he still rented an apartment in Woodbridge, Va., he invited his three siblings and their families over for the holiday, and spent two days cooking up old family recipes, including his late mother’s famous mac and cheese. It was a near-perfect day, Hunter said.

Like Bell, he wants to cook again for Thanksgiving. He wants to host his family again, especially his 12-year-old niece.

“I’m getting out,” Hunter said. “This is my first and my last,” he held onto the word for emphasis, “my last Thanksgiving here.”

O’Brien understood the sentiment.

A former Hollywood producer, he suffered a series of family deaths and medical issues four years ago, wandering to D.C. and ending up at the shelter as a resident. He “graduated” from the Mission’s work placement program after a year, and took a job with them as volunteer coordinator — though he still remembers what it was like when he considered himself homeless.

“I had nothing,” he said.

For the homeless, he said, the holidays are hard to get through. A hot meal is no panacea, but it helps. And on Thursday, that is what he and his dozens of volunteers were there to do: help.

Despite some delays due to a shortage of volunteers, it seemed by about 12:30 that everyone in Mission’s cafeteria had been served at least one plate of food. O’Brien paced nervously from one table to the other, looking out for newcomers.

“I’m just trying, you know,” he muttered, eyes furrowed. “I’m trying to make sure nobody goes overlooked.”

Michael E. Miller contributed to this report.