Sienna Miller Recalls the Moment Kevin Costner Asked Her to Join 'Horizon'

Sienna Miller recalls the surprising phone call from Kevin Costner that led to her role in the Western trilogy, "Horizon."

"I got a call. Be still my '90s heart," said Sienna Miller, 42, in an exclusive interview with Fox News Digital. "It said Kevin Costner would like to speak to you about a project that he's doing. I then got four scripts, so I was like, it must be TV. It wasn't. It's for movies. And then there's Kevin Costner on the Zoom, and I was beside myself. Anyway, we had a wonderful conversation. We got along very well. And at the end of it, he said, ‘Sienna, I have one question for you.’ And I said, ‘Yes, Kevin.’ And he went, ‘Will you go West with me?’ I died, I died."

Miller's excitement was palpable, as she had long been a fan of Costner's work, particularly his iconic performance in "Dances with Wolves."

Sienna Miller Recalls the Moment Kevin Costner Asked Her to Join 'Horizon'

"I had Cleopatra, Thumper, Badger, Two Socks and Cisco," she told Fox News Digital, referring to her pet rabbits named after characters in the film. "I was a huge fan of that movie. It broke my heart and [I] was very obsessed with Kevin from that moment forth."

Costner's visionary approach to storytelling, which Miller described as "almost like a novelistic approach to the journey of these characters," resonated with her. "I just like working with directors that take risks and are trying to challenge themselves in storytelling," said Sam Worthington, Miller's co-star in "Horizon."

Sienna Miller Recalls the Moment Kevin Costner Asked Her to Join 'Horizon'

While all four parts of "Horizon" chronicle the American West, Costner's narrative delves deeper, reflecting on the nation's history and its relevance to the present. "I think that Kevin is telling a story that shows that there was a lot of hope in how America was formed," said Worthington. "And therefore, if [there's] this hope in the formation of America, then maybe there's hope in the continuation of America – whether it's a Western or science fiction."

Costner's dedication to his passion project was evident throughout production. Miller shared that he was exceptionally supportive during her pregnancy while filming the second installment. "Kevin's so sweet," she said. "I told him I hadn't told many people, so he was constantly bringing me little snacks and drinks. I just needed to eat all the time. If I was eating, I was fine. But you know, a few nauseous moments behind tents."

Sienna Miller Recalls the Moment Kevin Costner Asked Her to Join 'Horizon'

Worthington praised the collaborative spirit on set, where everyone was "there for the right reasons to try and help him tell his story correctly." Miller and Worthington star alongside Luke Wilson, Abbey Lee, Jena Malone, and Giovanni Ribisi in the four-part Western saga.

With the first "Horizon" film set to hit theaters soon, Costner has shifted his focus entirely onto the saga, leaving his iconic "Yellowstone" character behind. "The time to step away was now," he told Fox News Digital.

Sienna Miller Recalls the Moment Kevin Costner Asked Her to Join 'Horizon'

Costner's commitment to "Horizon" is a testament to his passion for storytelling and his belief in the enduring power of the American spirit. Through his exceptional vision and boundless dedication, Costner has created a cinematic masterpiece that transcends time and speaks to the heart of what it means to be American.