When Caroline Weldon arrived at the Standing Rock Reservation in 1889, she attracted attention. The Sioux people who lived there hadn’t invited her. The white settlers who lived nearby didn’t understand why she wanted to go there. She herself was on the run from life as a social outcast in the East, her young son in tow.

But as she approached the encampment of Lakota leader Sitting Bull, she was confident in her mission: to help save the Sioux people from a government that wanted to take away their land and their way of life.

Weldon’s mission did not succeed, and she soon became a social pariah for her attempts to help the Sioux people. As the events that would ultimately end Sitting Bull’s life began to swirl, Weldon acted as his secretary and advocate, agitating for better treatment of Native Americans during a time in which bigotry against people like the Sioux was not just socially acceptable, but written into federal law.

“Weldon was one of the only white people of her time of either gender who not only had the right political view of Native American rights, but also gave her life to work for those rights,” says Eileen Pollack, author of Woman Walking Ahead: In Search of Catherine Weldon and Sitting Bull. The book, which details Weldon’s doomed, self-appointed mission to help Sitting Bull and the Sioux, was adapted into Woman Walks Ahead, a historical drama released in June 2018.

Weldon’s life was certainly movie-ready: She was an unconventional thinker and a woman who challenged the strict gender norms of her time. Born Susanna Faesch in Switzerland, she moved to the United States with her mother after her mother’s divorce. Susanna married a Swiss doctor and settled down in Brooklyn, but was unhappy and left her husband for another man, with whom she had a son. Her new lover left her soon after, and Susanna became a single mother.

These actions turned Susanna from an everyday Swiss immigrant into a pariah. The era’s strict gender roles meant it was nearly unthinkable for a woman to get a divorce, much less publicly raise an illegitimate child without a husband. Moreover, says Pollack, the terms of her divorce meant that, while her ex-husband could remarry, she could not.

Susanna had always been interested in the lives and rights of Native Americans in the United States’ ever-expanding westward territories. At the time, a debate raged over how to treat the nation’s Native people as white settlers flooded into the West. The United States created the first Indian reservations in 1851 with the Indian Appropriations Act, acknowledging tribal rights but driving Native Americans onto reservations where they governed themselves.

However, this was seen as a threat by a majority of Anglo-Americans, who felt that tribal loyalties could endanger white American values. Native Americans should become more “civilized” and begin to adopt their habits and customs, they argued, including adopting agrarian lifestyles and speaking the English language.

As this viewpoint grew in popularity, a tiny opposition was born. Susanna joined the National Indian Defense Organization, founded by Thomas Bland, which aimed to use U.S. laws to protect Native Americans and uphold their tribal sovereignty and land rights. The group opposed the Dawes Act, proposed legislation that would break many tribal lands up into individual plots and distribute them among tribe members, assimilate Native American children by forcing them into boarding schools, and take some tribal lands.

After the Dawes Act was passed in 1887, residents of Dakota Territory tried to extend similar provisions to the Sioux people who lived on land they wanted to occupy. When Susanna heard that Sitting Bull, leader of the Hunkpapa Lakota Sioux, was opposed to the plan, she began to write him letters. Then, in 1889, she decided to walk away from New York life to help him and live among the Sioux people. “She had nothing to lose,” says Pollack. “There was nobody left to shame, and she didn’t really care.” She also had a new name to indicate her new identity: Caroline Weldon.

As soon as she arrived at Standing Rock Reservation with her son, Weldon became a figure of amazement and mockery. She told Sitting Bull she wanted to be his secretary and representative and began to try to organize his supporters in the area to oppose the Sioux Bill. She also painted his portrait four times, using oil paints to capture the solemn face of the beleaguered chief.

Meanwhile, local newspapers picked up on the seemingly amazing story of a white woman traveling to live with a Native American tribe. They vilified Weldon as a harpy who was in love with Sitting Bull and called her his “white squaw.” That a white woman wanted to be associated with Native Americans, much less try to help them, was unthinkable to a country convinced that assimilation was in Native Americans’ best interests.

While Weldon was with Sitting Bull, a religious movement called the Ghost Dance swept through the area. The movement held that if Native people performed certain songs and dances, white people would disappear and their dead ancestors would rejoin them.

The movement was understandably popular among the Lakota Sioux, whose tribal holdings and unity were directly threatened by the Sioux Bill. Meanwhile, it was viewed as a threat by white settlers. Weldon warned Sitting Bull that it would turn him into a target, but he disregarded her. She began to advocate against the dance, causing a rift with Sitting Bull. Finally, she left the reservation. “They really meant a lot to each other,” says Pollack. “They each grieved terribly when they parted.”

Tragedy followed. Weldon’s instinct was right: A year later, U.S. officials arrested and killed Sitting Bull after he refused to stop Ghost Dance ceremonies on the reservation. Meanwhile, her son died and she returned to Brooklyn a social pariah for her association with people most white Americans loathed. She lived in poverty and died in obscurity two decades later when she was burned by a fire sparked by a candle in her apartment.

Weldon and her fellow activists were not able to halt federal policy that threatened Sitting Bull and the Lakota Sioux. The Sioux Bill devastated the Sioux people, reducing their land holdings and decimating their finances. And though Sitting Bull took advantage of Weldon’s assistance and she was welcomed among the Sioux people, she seems to have appointed herself their representative without consulting them.

Still, says Pollack, “It’s incredibly important to look at the very few people who in their time bucked all the conventions at great danger to themselves to do the right thing.” By advocating for Sitting Bull and a group of people most white Americans saw as expendable, says Pollack, Weldon “tried to make America live up to its own ideals.”