In the '70s setting, an orphaned boy who loses his hearing due to an accident, played by Oakes Fegley, runs away from his Minnesota home for New York. In 1927, the deaf Rose, played by Simmonds, escapes her overbearing father in New Jersey for New York, seeking a silent movie star played by Julianne Moore.
The film, richly evocative of different eras in film history, toggles between color and black-and-white, and between sound and silence.
Haynes and his casting director, Laura Rosenthal, cast the role of Rose via the deaf community, rather than choosing an actor playing deaf. Simmonds, from Utah, had no previous film experience but astonished the director with her audition tape.
"It was our incredible good fortune to find this girl, Millie, who from the very beginning the very first time I saw her tape I just shivered," he told reporters Thursday. "There was something about the integrity of her as a person that showed through that was true and ultimately you see it on the screen. Our good fortune in finding Millie can't be overstated."
Simmonds sat next to Haynes while a translator fed her sign language from the front row. She said "Wonderstruck" changed her life.
"It was such a wonderful story, I just re-read it. I'd go: 'Stop reading ahead. I have to focus on today's scene.' I just got lost in the story," Simmonds said, using sign language. "It was such an honor. I can't even find the words to explain what it was like to work with Todd. I never dreamt my life would come here, to this."
Roadside Attractions and Amazon Studios have given "Wonderstruck" an awards season release date, slating it for Oct. 20 in the United States.