The Duchess of Sussex surprised Williams with a video message that played on one of the massive screens around the stage, and she sweetly told the soulful singer that she's been supporting him all season.
"Hi Archie, I just wanted to let you know that we've been so moved by your story and we've been cheering you on every week, and it's not just because we're partial to the name," Markle said, referring to her and Prince Harry's 1-year-old son, Archie.
"So, a very special message to you -- [which] I will probably be saying all my life, but on this night it is specifically for you -- Archie, we are proud of you, and we are rooting for you, and we can't wait to see what you do," Markle added. "We're in your corner! Have a good night."
Markle's video got Williams choked up almost immediately, but the singer had a very emotional night even before the surprise message. Williams has been one of the most talked about and celebrated performers of the season, both because of his undeniable talent, but also because of his incredible story of perseverance.
Singing was one way he managed to stay hopeful during his decades behind bars, and the songs of gospel icon Marvin Winans played a particularly significant role in his love of singing. So, for the finale, AGT gave him the chance to perform a duet with Winans, and Williams couldn't fight back his tears.