Mandy Moore almost didn’t make it to This Is Us. The teen icon and musician was coming off of years of rejection, a string of network pilots that didn’t make the cut and B movies that met critical derision and worse at the box office. She hated auditioning. She hadn’t released an album in almost a decade, despite first finding fame as a singer, and considered turning away from the entertainment industry.

But fate has a way of intervening. The This Is Us pilot came her way at a low point and promised something different—she just needed to nab the part, and from there, for NBC to pick the show up to series. “My heart has been broken repeatedly for the last four years by this world,” Moore recalls telling her team after receiving the script. “I don’t know if I’m strong-willed enough to face another sense of rejection.”

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There’s a lot, it turns out, Moore didn’t know about herself going into This Is Us. That goes for viewers too—put bluntly, the former teen idol isn’t who most would think of for a role like Rebecca Pearson, which ultimately demanded so much emotional depth, dramatic range, and technical precision. Yet from the moment Moore showed up on the pilot’s set to film her two days’ worth of scenes, she felt determined to give it everything she had. “I’d heard [she’d been] questioning sticking around acting, and I think she went into it just not ready to let it go,” recalls Milo Ventimiglia, who plays her husband, Jack. “She had a bit of a fire, a bit of unfinished business with acting, going into the whole series six years ago. I saw that really quickly in her.”

Over its six-season run, which concluded Tuesday, This Is Us became one of TV’s most popular shows, unfurling constant twists in its epic, time-hopping portrait of a complex American family. Moore’s Rebecca proved central to the ambitious conceit—with her powerhouse performance increasingly essential to its success. Rebecca exists in one timeline in the pilot, a 30-something mother beset by tragedy and then a miracle. As the series continues we come to know her as a teenager, a new grandmother, and an older woman approaching the end of her life—sometimes, all in the same episode, with Moore portraying her at each age. The actor had no idea this was the plan upon signing on. “Had I been told going into this audition, ‘This is what the show is going to be, this is what you can expect,’ I would’ve been like, Oh no, no, no, no,” Moore tells me. “I can’t do that. I’m a 31-year-old woman. There’s no way; I have no life experience. I don’t have the bandwidth to even imagine what any of that would be.”

Moore expresses a sense of gratitude repeatedly during our conversation. Over Zoom, she’s warm, thoughtful, and clearly emotional, tearing up in a few instances as she continues to reflect on the project that changed her life. (“I feel overwhelmed,” she says early on.) Not only did This Is Us come to her at the right time, but it was presented in the right way to convince her to give it one more go. Dan Fogelman, the creator of This Is Us, got to know Moore in the animated hit Tangled, which he wrote and for which Moore voiced the lead role of Rapunzel. He saw in her what others didn’t. “She’d been famous for a really long time at a very young age, she held herself together normally, personally, but had this kind of quality about her that led people to keep casting her in romantic-comedy parts,” Fogelman says. “There was something about her that I always felt could go much deeper and a little darker if required—really heavy material that she hadn’t yet explored as an actress.”

Moore’s persona plays into the way we meet—and, in the final season, say goodbye—to Rebecca Pearson. The young mother is ebullient, with a brilliant smile and a boisterous laugh. It’s the Mandy Moore we know, at her most appealingly familiar. Episode two then punctures expectations: There’s the actor in a new wig and old-age makeup, the character now in her late 60s. This Rebecca speaks in a hushed hurry, carrying decades of regret over her now slightly arched back, as she navigates grandparenting and a second marriage. Is this a gimmick gone very wrong? As Moore holds her adult children—played by Justin Hartley, Chrissy Metz, and Sterling K. Brown, all of whom are older than her in real life—in an intimate maternal gaze, she slowly holds us there too. It’s mesmerizing—and, frankly, bizarre. The longer you stick with it, the more remarkably convincing—invisible, really—Moore’s transformation becomes.

Ventimiglia tells me that, before cameras started rolling, he and Moore would sit for a moment, “look square in one another’s eyes, and we were right there with Jack and Rebecca. Didn’t have to stray too far, didn’t have to do too much. It was all right there.” Moore speaks of her prep similarly, no matter the task of the day. She found an ease with incredibly complicated material, and came to embody the show’s tearjerker bona fides better than any actor on the show: her weepy fury through Rebecca and Jack’s epic fight in the season one finale; her otherworldly wail as Rebecca’s pain in widowhood comes to the fore after a new grandchild is born; her heartbreaking sensitivity charting Rebecca’s Alzheimer’s decline in the especially wrenching final season.

She didn’t stand out immediately; Brown and Ventimiglia, particularly, found more awards recognition early on. But over time, Moore took charge. Fogelman and director and executive producer Ken Olin got used to watching in awe. “We’d sit there and go, ‘What the fuck is she doing? How is she doing this?’ And I don’t really know what her secret is,” Fogelman says. “I’ve never completely understood how she’s doing it.”

After finding pop stardom as a teenager in the late ’90s, Moore pursued a Hollywood career, reaching commercial success in projects panned by critics, most notably the romantic melodrama A Walk to Remember. Her screen talents were put to funnier, spikier use in comedies like The Princess Diaries and Saved!—she portrayed indelible mean girls, sharp-tongued antagonists in both tales of teen angst and triumph. Quite a jump from the girl-next-door, top-40 singer who went platinum at age 15. This was where Moore pushed herself as an actor, showing the grit behind the charm. It wasn’t half-assed either; the performances resonated in their vicious believability.

While watching This Is Us, I’ve thought back to that unshackled teen Moore, knowing a tough role inside and out. Her on-camera intuition has long been undeniable, if oddly unsung, and that quality has defined her time on the NBC drama. “You would think Mandy would’ve had a lot of ideas and questions and concerns, exploring something this deep, but from my end, she just showed up and did the work,” says Fogelman. Moore reiterates this for me. She trusted the writing, and went with it.

Moore had known for a few years about the Alzheimer’s arc that would wind down Rebecca’s story, and periodically checked in with Fogelman on hitting specific story beats and the reasoning behind sensitive character moments. Playing the disease, as a woman in her 30s who hasn’t been personally touched by it, marked her greatest challenge on This Is Us. Before every episode exploring Alzheimer’s, then, Moore did her homework: calls with a neurologist to double-check plot points, shifts in facial and vocal patterns, considering every meaning of a line in the context of Rebecca’s mental state.

“Even those parts that didn’t make it into an episode…I just wanted to make sure that we have all of our bases covered,” Moore says. “It also comes down to the performance and that’s something that’s really been top of mind for me as well. I didn’t want it to feel like this caricature of what people are experiencing. I tried my level best to do as much homework as I could do, to make sure that people felt like, yes, that is very true to what I have experienced and what I have witnessed.”

The final episodes of This Is Us hinge greatly on what Moore brings to each version of Rebecca; the whole show is sold, ultimately, on her authentically playing something well beyond her experience, not to mention her past roles. Fogelman only went through with the Alzheimer’s story line because Moore had proven she could do it. “We just knew we had the actress who could pull it off believably and make you feel all of it—the young, glowing version of her who was magic, and the older version, who’s still there, but is just very different and altered all the way to the very end,” he says.

Moore has found it difficult to let go. After reading the penultimate episode of the series, in which Rebecca dies, she vomited suddenly. In fact, she read it five or six more times, and became overcome, over and over—this purge of saying goodbye to something that meant everything. Even now, reflecting on reading the script again, she gets emotional. “It was just my body’s reaction to, I think, this is the end and this is over—I cry thinking about it,” she says while choked up. “I just remember thinking, How am I going to do this?” Of course, she managed. Ventimiglia, who spent more time this past season watching Moore off-camera, told her quite simply on set, “I’m proud of you.”

He wasn’t alone. Loud calls for Emmy recognition are coming from inside the house. (Moore was nominated once before, in 2019.) Best-actor champ Sterling K. Brown all but launched a campaign for his costar on Instagram; Fogelman speaks of her now in awestruck terms: “I think Mandy Moore has done something in this show, particularly in these past seasons, that maybe has never been done at this level for this amount of time, with this amount of import, in a show that’s this watched—ever: Traversing timelines in this many age ranges believably, to the point where people are commenting on the performance of a character and a timeline without even recognizing that they’re talking about a 35-year-old woman playing a 70-year-old woman with Alzheimer’s disease.”

Indeed, it’s an unusual, once-in-a-career kind of showcase. “I am fully confident that no other job will fulfill me quite this way. It’s checked every box,” Moore says. “I know that nothing else is going to be this and I’m fully prepared for that. And that’s why it’s so sad to say goodbye in every respect, but it also makes the future really exciting.” (In terms of music, she also has a new album out, and is set to tour for the first time in 15 years.)

So onto the next acting job? “I’m not going to sit through four hours of prosthetic age makeup to play the same character again. I have fulfilled that. So what serial killer can I play?” She laughs—a joke about the unknown as to what’s next. But oh, there’s that sense of possibility again too.