Naomi Watts says she feels 'horrible' her late co-star Treat Williams won't get to see his final performance

LOS ANGELES, CALIFORNIA: Naomi Watts paid a heartfelt tribute to her late co-star Treat Williams ahead of his final performance.

The actress played Williams' on-screen wife in the upcoming second installment of the 'Feud' anthology series by Ryan Murphy.

How did Treat Williams die?

On June 12, 2023, Williams tragically died in Vermont following a motorcycle accident after filming for the 'Feud' anthology series.

"It's truly heartbreaking because he had such gratitude for this role at this point in his life," Watts told ET on Tuesday, January 23, at the series' premiere event in New York City.

"I mean, we all did because the writing is so delicious... but Treat was just-- He couldn't believe it. Every day he was like, 'Oh my god, these words!'" she continued.

Naomi Watts recalls 'how happy' Treat Williams was on the set

In the upcoming installment titled 'Capote vs The Swans', Watts stars as Barbara 'Babe' Paley, a magazine editor socialite while Williams plays her husband William Paley who is a CBS executive.

"In between the scenes that we were making, he just talked endlessly about how happy he was and about his beautiful family and his dogs and living in Vermont," Watts said of Williams.

"It's really horrible that he won't get to see this and see us all celebrate his work," she added.

What is 'Feud: Capote vs The Swans' all about?

The series focuses on the conflict between Truman Capote, played by Tom Hollander, and a group of New York socialites.

The tension arises after Capote writes a thinly disguised retelling of group of socialites' sordid drama in his posthumous 1986 novel 'Answered Prayers.'

Naomi Watts opens up about portraying Barbara 'Babe' Paley

Watts' character Paley who was a fashion editor at Vogue was renowned for her sense of style and was often featured on 'Best Dressed' lists of her time.

Speaking about her transformation into her character, Watts said, "it's fun."

"I really only had pictures to go from -- there was no videos or audio recordings, so I really studied these pictures and looked at the way she moved," she continued.

"Where her hands were placed, how she did her hair, and they told a lot of story. Her focus and passion for fashion was always there. It's a lot of pressure though to have to look that good and that pristine all the time," she added.

'Feud: Capote vs The Swans' premieres January 31 on FX with episodes streaming on Hulu on February 1.