Listen to the Emotional Song Rebecca Performs at Kate and Phillip's Wedding

"It's going to get bad," This Is Us writer Kay Oyegun told NBC Insider a few weeks back when asked about how Rebecca's (Mandy Moore) Alzheimer's progresses throughout Season 6. "Objectively, unapologetically, it’s going to get bad. Point blank, period. This is a disease that kills many people, ruins many families."

That statement was difficult to swallow, but Oyegun wasn't exaggerating. Rebecca's Alzheimer's is getting worse, and viewers saw that most clearly in Season 6, Episode 13, titled "The Day of the Wedding." The episode is centered around a happy occasion, Kate (Chrissy Metz) and Phillip's (Chris Geere) wedding, but the tone is much more somber. Sprinkled throughout the day's festivities are signs Rebecca's memory is only deteriorating. On multiple occasions she brings up Jack (Milo Ventimiglia) as if he's still alive. At one point, Kevin (Justin Hartley) walks into the room, and Rebecca sees him as Jack. It's clear the family is processing these developments in different ways. In Kate's case, she's acutely petrified because Rebecca is supposed to sing a song at her and Phillip's reception. But will she be up for that? 

"Once she finds her key, she'll lock in," Phillip tells Kate. It's a mantra used throughout the episode—and thankfully, that's exactly what happens. Rebecca does find her key at Kate and Phillip's reception, beautifully performing her song and moving everyone to tears. 

The lyrics of the song, in a way, speak to where the Big Three are all at now. In a speech at the reception, Randall (Sterling K. Brown) talks about time zooming past them and wishing it would slow down. As Rebecca's condition worsens, that desire becomes stronger and stronger. "The years can be counted in seconds," Rebecca sings on the track. "That's fine with me, 'cause I get this moment with you forever now. " Listen to the full song, titled “The Forever Now,” in the video, above. (The song was written by Siddhartha Khosla and Taylor Goldsmith and is available on streaming platforms. And if it sounds familiar, that's because it is. The piano riff actually mirrors the This Is Us closing theme music.) 

The Pearsons want to hold tight the time they have left with Rebecca—and fans want to hold tight what's left of This Is Us. We only have a few more episodes left. Get ready. 

This Is Us airs Tuesdays at 9 p.m. ET on NBC. Catch up now on NBC.com.