Mandy Moore Discusses 'This Is Us' Rumors and What's Ailing Rebecca

"I do know what’s ailing her," Moore said of her character on the hit NBC series.

In the season three finale of NBC's hit drama This Is Us, audiences were left with a flash-forward shocker, showing a much-older Rebecca (Mandy Moore) bedridden and silent, with Jack's estranged brother Nicky (Griffin Dunne) at her feet, as Randall (Sterling K. Brown) enters the room and introduces himself as her son.

Since then, viewers have been throwing around theories as to what’s happened to Rebecca, with some suggesting Alzheimer's or dementia. Mandy Moore discussed those rumors during a sit-down with The Hollywood Reporter In Studio, revealing that she does know "what’s ailing" her character.

"I can't confirm or deny anything," she said of fans theories. "It feels so weird to be on a show with these sorts of secrets and stuff. I mean, I think it's part of the storytelling device. You don't want to give anything away, and I think over the course of, now we have the next three seasons, we know to parse out this information. And I think Dan [Fogelman] is very specific how we tell the story and when these bits of information are disseminated and I respect that."

She added: “I think you know I can't say that I've necessarily seen exactly what's ailing Rebecca, like out in the ether necessarily, but I will say it was a really bittersweet moment on set to shoot that particular scene with Sterling and with Griffin Dunne, and just to be in that frame of mind of where Rebecca is potentially towards the end of her life."

With season four of This Is Us returning this fall, Moore opened up about where she hopes to see Rebecca's story going, saying, "I am excited to sort of revisit lighter times."

"I'm psyched to get back with Milo [Ventimiglia] and do early Jack and Rebecca courtship. I've heard that we're going to pick back up," she explained.

"We saw this pretty epic road trip out to California last season with Jack and Rebecca, and the record label, and her failed music career, and them deciding to, in spite of everything, maybe couple up and head back home to Pittsburg. So, I'm curious what their relationship is once they get home, and he's clearly still reeling from PTSD from the war, and how her parents are going to accept him in her life, and just the very dynamics that make up the relationship and how they found their way to being the couple we know them to be now."

Watch the video above to hear Moore also working on brand-new music, exploring Rebecca and Miguel’s [Jon Huertas] relationship on This Is Us and more.