In 1930s England, a determined and compassionate woman named Gladys Aylward feels a calling to serve as a missionary in China. Despite being turned away by the official mission board due to her lack of education and funding, she perseveres and eventually secures passage to the remote province of Yang Cheng. Upon arrival, she is welcomed by an elderly missionary named Jeannie Lawson, who runs an inn catering to travelers. Together, they plan to use the inn to spread Christian teachings and local customs among the villagers. When Jeannie passes away, Gladys has to rely on her wits and bravery to continue their mission alone, gradually earning the trust and admiration of the local people.

As war looms over China and the Japanese army advances, Gladys finds herself drawn into the conflict. She takes on increasing responsibilities, including helping the local Mandarin implement social reforms and rescuing abandoned children. Her courage and compassion resonate deeply with those she helps, turning her into a symbol of resilience and hope in a time of turmoil. The villagers, officials, and the children she saves all look to her as a beacon of light amidst the darkness of impending war.