Daisy Ridley stars as Gertrude "Trudy" Ederle, the accomplished swimmer who was born to immigrant parents in New York City in 1905. Through the steadfast support of her older sister and supportive trainers, she overcame adversity and the animosity of a patriarchal society to rise through the ranks of the Olympic swimming team and complete the staggering achievement – a 21-mile trek from France to England.