Melissa Fitzgerald, formerly of “The West Wing,” volunteered with Justice for Vets and was surprised when the advocacy group offered her a job. (Deborah Jaffe/For The Washington Post)

We’ve seen it before: A Hollywood actor finds a cause, jets to Washington for a photo op and a handshake, makes a speech and flies home.

This is a story about a Hollywood actor who found a cause, then jetted to Washington, then moved to Washington, then got a job at a nonprofit group in Washington and then one morning found herself having meetings at the Pentagon, where some of the other attendees had no idea who she was.

Her name is Melissa Fitzgerald. She was on “The West Wing.” She played — well, we’ll get to that. First, the Pentagon. In a wood-paneled conference room, someone cues up a PSA in which fellow “West Wing” alums, as a favor to Fitzgerald, publicize the organization she now works for, Justice for Vets. On-screen, Bradley Whitford, Allison Janney and other cast members discuss the benefits of treatment courts for veterans who fall into legal trouble. The PSA finishes. An Army lawyer has a suggestion.

“You should go back and digitally put yourself in some scenes in ‘The West Wing,’ ” she jokes with Fitzgerald. “Because everyone else in the PSA was in it!”

Fitzgerald, 50, smiles apologetically. “Oh — I was. I was in it.”

“You were? Oh, my gosh. I didn’t know.”

“I knew, but I wasn’t going to say anything,” the lawyer’s colleague confides.

“So you’re famous?” the lawyer asks.

“I played Allison Janney’s assistant.”

CAROL! She played Carol. The unflappable right-hand woman to press secretary C.J. Cregg, seen in most episodes managing her boss’s work and love life.

After two decades in Hollywood, Fitzgerald now lives a very Carol existence. She has an apartment in Alexandria, Va. At work she has a small, gray office in which she keeps spare cardigans. She sometimes brings muffins for the communal kitchen, which has dirty dishes in the sink, like office kitchens everywhere.

“And emails,” she sighs, gesturing to her computer a few days after the Pentagon meeting, while she and a colleague figure out which contact list to use for a newsletter. “Do most people get 150 emails a day?”

In a roundabout way, this is Martin Sheen’s fault.

Sheen, who played “The West Wing’s” fictional president, had been a longtime advocate of the National Association of Drug Court Professionals, the umbrella organization of which Justice for Vets is a part. Sheen knew that Fitzgerald was an activist herself — the University of Pennsylvania graduate had founded a mentoring program in Los Angeles and produced a documentary about child soldiers in Uganda — and he also knew that Fitzgerald’s father was a Philadelphia judge who supported treatment courts in lieu of traditional prison sentences. In 2011, Sheen asked whether Fitzgerald was interested in coming along to the annual NADCP meeting. The stories she heard there moved her; she ended up volunteering and then co-producing another documentary, about the struggles of veterans returning home.

Fitzgerald, left, played White House aide Carol on “The West Wing,” and many of her scenes looked like this, reacting to some sharp repartee from Allison Janney, right, as press secretary C.J. Cregg. Actor Timothy Busfield is at center. (Warner Bros.)

One evening a few years later, Fitzgerald was talking on the phone with the NADCP’s then-chief executive, West Huddleston. He mentioned that his senior director, an ex-Marine, had just resigned and that he needed a replacement to help expand the existence and role of treatment courts nationwide. “If I were a veteran, I’d throw my own hat in the ring,” Fitzgerald said offhandedly. A few days later, Huddleston called back. Was she serious?

Fitzgerald thought about it. “The West Wing,” her most recognizable role, had ended several years before. She was still acting, but mostly in smaller parts. As often as not, she was skipping the auditions that did come up so that she could go do activist-related work elsewhere around the country, which her agent told her was getting “demoralizing.”

She made a few phone calls.

She called Patrick Murphy, an old friend who is now the acting secretary of the Army. Did he think servicemen and women could respect someone who had never worn a uniform? “I told her that the Army and military desperately needed her leadership at this time,” Murphy remembers. The gap between civilians and servicemen seemed to be widening. “We can’t do this alone,” he told her. “We need someone to bridge the civilian-military drift.”

She talked to Janel Moloney, who played fellow assistant Donna on “The West Wing”; Fitzgerald is now the godmother to her son. “She needs to do something meaningful with her days,” Moloney says about her friend. “She’s always been that way — she needs it in order to survive.”

She called Huddleston back. He said, “When can you start?” She said, “How about January?” He said, “How about Monday?”

The job would mean a pay cut from her most productive years in Hollywood. Then again, an actor who kept skipping her auditions to do activist work had an annual salary of zero dollars. More important, Justice for Vets seemed like a place where she could work on an important issue and be useful.

Huddleston wanted her to begin in time to be introduced at an upcoming convention. Fitzgerald got on a plane and came to Washington to meet with Chris Deutsch, the organization’s communications director, who had prepared a few remarks for her to give.

“I honestly didn’t know what to expect,” Deutsch says. He’d been skeptical of Fitzgerald’s hiring and wasn’t sure whether she would be mostly a figurehead, or a spokeswoman, or what, exactly. But then she came to him with a marked-up copy of his speech: She’d stayed up all night revising it and wanted to make sure it was exactly right. “That was the moment I realized she was for real.”

This is also a story about bubbles. How Hollywood is one. How Washington is one, too, in its own way. When Fitzgerald lived in Los Angeles, she had a sunny house in the chic Beachwood Canyon neighborhood and jobs in which her work clothes were costumes selected, ironed and laundered by professionals. When she moved to D.C., she had a one-bedroom apartment three blocks from her office. No furniture; she’d shipped herself a box containing an air mattress and a coffee maker. Her first night in the apartment, she went to bed, and it deflated to the floor. She got out of the air mattress. She took an Uber to Target. She bought a new air mattress. She started arriving at work at 8 a.m. and leaving after 8 p.m. This was now her life.

Fitzgerald meets with colleagues Liz Dawson, left, and David Pelletier at the Justice for Vets office in April. “I had never done a PowerPoint” before moving to Washington, she said. (Deborah Jaffe/For The Washington Post)

“Someone sent me an email that said, ‘Can I have your answer by COB?’ ” Fitzgerald says. “I asked Chris, ‘What’s COB?’ He said, ‘You have lived a very good life if you don’t know what COB is.’ ”

Actors work long hours. But nonprofit Washington is defined by not only the exhaustion of long hours but also the complications of paperwork, red tape, PowerPoints (“I had never done a ­PowerPoint,” she says) and time cards (“I said, ‘Wait a second, I have to fill out a time card?’ ”).

“The West Wing” was one of the few shows that got the bubble of Washington exactly right. It was fervently beloved in its day and, weirdly, nostalgically beloved even now, a decade after its last episode aired. Washingtonians still stop Fitzgerald to thank her for the show; it’s hard to imagine that a supporting actor from, say, “NCIS” would be able to use her screen time to launch a wonky policy-related career.

After Huddleston offered the director job to Fitzgerald, “I got a lot of pushback,” he says. “A couple of folks said she’s an actress who has no connection to veterans and will have no credibility. I said, ‘You know, it’s so nontraditional that we’re actually going to get some attention.’ ” He had interviewed traditional candidates, but none of them had the passion and “fearlessness” that he thought Fitzgerald did.

(It should be noted that in “The West Wing,” Fitzgerald was a ­buttoned-up background player, channeling an ordinary administrative assistant. In person, she is a frequent laugher, a passionate speaker and reliably the most magnetic personality in a room, with very good hair.)

Fitzgerald attending the Human Rights Campaign National Dinner in Washington in October. (Erin Schaff/For The Washington Post)

In her Alexandria office in April. (Deborah Jaffe/For The Washington Post)

Now her real-life role looks occasionally similar to her former on-screen life: She has an office wardrobe, composed in large part of clothes from a designer she sought out because she remembered the labels from her Carol wardrobe.

She has staff meetings.

“Okay,” says her boss Carson Fox, the NADCP’s current chief executive, at one such staff meeting, which was called to plan a summer conference. “So we’re doing the color guard and then the intro?”

“Yes, I think you have to start with the color guard,” Fitzgerald agrees.

“Let’s see if we can find a really good keynote,” someone else suggests.

“We can talk about who we want and see if it’s someone I know,” she offers. “And I don’t mind having the keynote in the beginning.”

She has conversations like this:

“I have a call on Monday at 10 a.m. with the head of the Triumph Games, and she would like to find a role for us, which would be great,” she says to Deutsch when he stops by her office.

“That’s great,” he says. “When you get a chance, can you shoot me the final draft of your speech?”

“Will do,” she says, and then she turns back to her computer.

It is lit by the soft glow of a fluorescent light panel overhead, and it emits the sound of emails coming in at frequent pings.