In ‘Long Bright River,’ Amanda Seyfried Serves and Protects

For Amanda Seyfried, the first day on set for “Long Bright River,” a limited series for Peacock, was awful. She stood under the lights in a mock-up of a police morgue, in her patrol cop uniform, unsure how to move or speak.

“Every first day of work, I never know what the [expletive] I’m doing,” she told me later.

Seyfried overprepares for most roles. She researches; she memorizes; she asks question after question. But then suddenly she’s on a soundstage somewhere, with the lights blazing and the cameras pointed at her face, and the terror rushes in. If she has an acting process, she said, “it’s all based on the fear that I’m not going to be good enough.”

Seyfried, 39, was speaking on an icy February morning. We’d met for a late breakfast at a cafe on the Upper West Side of Manhattan, near where Seyfried keeps an apartment. (She and her husband, the actor Thomas Sadoski, and their two children, spend most of their time on a farm upstate.) She was in town to shoot a Paul Feig movie, “The Housemaid,” and to promote “Long Bright River,” a moody eight-episode suspense series that premieres on March 13. She had recently wrapped “Ann Lee,” a historical musical by Mona Fastvold.

Does this sound like a lot? It was. “I think I’m falling apart,” Seyfried said as she looked at the menu. She had recently injured her back on “The Housemaid” and was taking muscle relaxants.

“I’m fine now,” she said. “I mean, I’m not. I’m struggling, but I’m walking.”

Seyfried has been in the business for more than two decades, and has moved, gradually, from comedy (“Mean Girls”) and romance (“Mamma Mia”) to more complex roles. Her performance as the actress Marion Davies in the Netflix film “Mank” earned her an Oscar nomination, and she won an Emmy for her portrayal of the convicted fraudster Elizabeth Holmes in the Hulu mini-series, “The Dropout.” With those roles and those accolades secure, she has finally been recognized as a gifted dramatic actress.

It makes sense that Seyfried spent so many years mostly in lighter fare or ingénue roles in heavier material (“Big Love,” “Les Miserables”). She has limpid, wide-set eyes, a heart-shaped face, rippling blond hair. Even at a corner table, dressed down in a winter coat and plaid scarf and obviously exhausted, she looked like she should be posing on a scallop shell somewhere. But behind those sweetheart looks is a transformative actress keen to show the world what she can do, even when it scares her — especially when it scares her.

“That’s the part of me that I have to honor,” she said. “Anything you care about, you’re going to be afraid.”

I had seen Seyfried on the “Long Bright River” set a few months before. Seyfried plays Mickey, a Philadelphia beat cop and a single mother. Mickey spends the series searching for her sister while also investigating the murders of vulnerable, unhoused young women in Kensington, a Philadelphia neighborhood. That day, Seyfried was dressed in plainclothes — a gray sweater, jeans — doing light calisthenics as she prepared for an emotional scene in which Mickey comes home to discover that her son is missing.

“If you want to get emotional or really intense in a scene you do lunges,” she said then, switching legs. “I have no cartilage in my knees, but it’s worth it to me.” Not everyone would discuss their cartilage with a reporter, but this was Seyfried — earthy, outspoken, dryly funny.

“Amanda is so undeniably raw, and she’s like a magnet,” Nikki Toscano, a showrunner on “Long Bright River” said. “You want to be near her. You want to hear what she’s going to say next.”

Small and slight, Seyfried does not seem like a natural fit to play a cop. Then again, she also wasn’t an obvious choice to play a medical technologist (“The Dropout”) or a principled psychotherapist (“The Crowded Room”). But savvy actors and producers have always known that she is capable of more.

“She is formidable,” said Akiva Goldsman, the creator and showrunner of “The Crowded Room.” “For a compact human, she has a giant ability to move the air in the room.”

On “Long Bright River,” Seyfried is meant to be an odd fit, because Mickey — a quiet, troubled woman who unwinds by playing the English horn — is an odd fit for the force. According to Liz Moore, the showrunner who wrote the book the series is based on, Seyfried’s slight frame suits the role. “It’s a physical expression of the fact that Mickey knows she’s maybe not supposed to be doing police work,” Moore said. Seyfried’s presence helps to upend the narrative of cop as savior or hero.

Seyfried has wanted to play a policewoman — not a detective, she specified, a beat cop — for years.

“I’m a tiny little tiddlywink, a tiny baby,” she said. “But even tiny babies can play cops. I just wanted to prove to myself that nothing can feel too foreign.”

Still, she couldn’t find a role that worked. Then a producer on “The Dropout” suggested that she look at “Long Bright River.” So she listened to the audiobook. (Seyfried is an audiobook fiend and usually has four or five titles going at once.) She knew that she could play Mickey. Later, she would also learn to play the English horn.

Mickey, who lives in the shadow of a traumatic upbringing and who works a job she isn’t especially good at, was unlike her in many ways. But there were similarities. Seyfried grew up in Allentown, less than an hour from Philadelphia, and she is close to people who have been directly affected by the opioid crisis.

“I know the people in this story,” she said. “I felt confident that I could ground it.” She understood Mickey’s devotion to justice, her need to protect the people around her.

To prepare, she met with volunteers and activists who work with members of the Kensington community. She also did a ride-along with two Philadelphia cops, both of them single mothers like Mickey. She noted their compassion, the way they declined to impound the car of a new mother. While performing a wellness check, the officers discovered a dead body. “And I was like, real life, this is real life here,” she said.

To bring that reality into the container of a streaming thriller was the challenge. Going in, she’d had a few ideas — how she might hold her shoulders, how she might walk. But by the second week, once the terror had eased, she let that all go. As Mickey, she looked, she knew, “like a little girl lost in a uniform,” so she would play that as faithfully as she could.

It worked, at least for her co-stars. “When the camera was rolling, I couldn’t see Amanda,” said Nicholas Pinnock, who plays Mickey’s former partner. “There’s a truth and an honesty in what she does, which is unapologetic.”

In conversation, Seyfried does do a fair amount of apologizing — for rambling, for digressing. But she knows who she is and after the first day or two of any given shoot, she knows that she is good at what she does. “There’s a genuine joy in her work,” said Elizabeth Meriwether, the creator and showrunner of “The Dropout.”

At the restaurant, late into the meal, “Honey, Honey,” from the “Mamma Mia” soundtrack began to play, with Seyfried’s 22-year-old voice issuing through the restaurant’s speakers. The waitress came over, contrite. The song was just part of the usual play list.

“Listen, I love having a stake in pop culture,” Seyfried reassured her. “It’s really nice.”

With an Emmy win under her belt and subsequent projects wrapped, Seyfried finally feels like she has a place, for as long as she wants it, in the business she loves. It doesn’t mean that she doesn’t want to change or grow or stretch herself. And that fear, she’s pretty sure she’ll always feel it.

But she knows she will always work. It took a long time for the industry to take her seriously, consistently, as a dramatic actress, but now it has. “It felt fleeting for so long until it didn’t,” she said.

Despite the exhaustion, she already has further projects lined up — an erotic thriller via Meriwether, an Erica Jong biopic for the director Rebecca Hall. She doesn’t want to write or produce or direct; she just wants to keep giving herself over to one difficult character after another, in and out of uniform.

“I’m not going anywhere,” she said. “I’m already kind of where I want to be.”