Any good Catholic—or Catholic survivor—can tell you how much their lives were shaped by nuns. What may surprise the rest of us is how society as we know it today has been molded, radicalized, and entirely transformed by them, too.

“Can you smell the pot?” Lenore Dowling asks her friend from the Immaculate Heart Community, the two counting as joyful and passionate, sign-wielding participants at the 2018 Women’s March in Los Angeles.

The pair are no strangers to the spirit of protest, nor to the skunky accoutrement that tends to waft through its surroundings. Within them, that spirit has been downright holy for decades, since they first took their sacred vows as nuns—and then, later, when they felt compelled to request a dispensation from them.

“We were nuns,” Dowling says in that first scene that sets up Rebel Hearts, a new documentary that premiered at the Sundance Film Festival on Jan. 29. “I joined to be a nun. We were Sisters of the Immaculate Heart of Mary the Blessed Virgin. Then we got into trouble with a bishop…”

The ellipsis teases a rewinding of the clock that goes back eight decades, underscoring the friction that triggered a crisis of conscience and of faith for an order of progressive nuns who felt their autonomy and rights as women shouldn’t be at odds with their holiness—a suggestion with which the Catholic Church fundamentally disagreed.

Rebel Hearts is an invigorating and, at times, revelatory history of their fight: to oversee a radical California women’s college in the 1960s, transform the education system, challenge the church’s antiquated and misogynistic doctrines, and, at a time of kinetic change and social evolution, confront the patriarchal nature of their faith, the institutions to which they pledged, and the culture in which they sought to make a difference, issue by issue and march by march.

Directed by Pedro Kos with great admiration for the women whose stories he’s telling, the documentary opens by characterizing how the media portrayed the women of the Immaculate Heart in the ’60s as their clashes with the Los Angeles archdiocese, its cardinal, and even the Vatican began to make headline news.

They were called “defiant” and accused of staging a “nuns’ rebellion.” LIFE magazine published a cover with the headline: “The Pope’s Unruly Flock.” It’s not what you expect to hear about the women who take a vow of poverty, chastity, and obedience, and marry themselves to Christ.

But those constraining expectations based on a habit and a vow were precisely what the Immaculate Heart nuns were out to explode. And with that, they provided a spiritual backbone for one of the country’s most formative decades of social unrest and progress.

As articulated by Corita Kent, a pop artist who left the sisterhood in 1968, “Changing is what keeps one growing.” Two years later, 315 other nuns also left when their demands for dignity and evolution weren’t met.

There’s a certain whimsy to archival footage of nuns in their habits buzzing around a convent. Rebel Hearts leans into that as it takes the timeline back to the 1940s to explain why so many of the documentary’s subjects, now either passed or in old age, were attracted to Immaculate Heart in the first place.

It may come as a surprise that, for many of them, joining the convent was a way to assert their independence as women.

Kos cleverly establishes time through old magazine clips, advertisements, and commercials. In the case of the 1940s, those mediums laid out the American woman’s fate as a homemaker. Immaculate Heart was a way to escape that destiny.

It was a means of getting an education. It was a vehicle to be of service. Plus, the nuns at Immaculate Heart College, which was run by the convent, were strikingly modern. They’d drink a Coke if it was offered to them. Snack on potato chips, too.

Motivated by that yearning for independence, many of these women bristled at the strict ceremony and regimen of life in a habit: All sisters must obey prayer schedules. Sisters must keep silent during the day. All sisters must be in the convent by 6 pm. Learning how to deep clean was a path towards holiness. All of it meant to instill the instinct to obey.

Many of the sisters read a 1961 book called Asylums by the sociologist Erving Goffman and “realized the same kind of restrictions that were put on people in mental institutions were the same kinds of rules that controlled our lives,” says Pat Reif in the film, one of the Immaculate Heart nuns at the time.

The best thing Rebel Heart does, with few exceptions, is allow the nuns to tell their stories themselves. In addition to Reif and Dowling, former nuns Anita Caspary, Helen Kelley, and Patrice Underwood serve as narrators, explaining how the circumstances of their awakenings—both spiritual and as women in society—led to the most intimate and consequential decisions of their lives: to leave the sisterhood.

Their decision came after a veritable war of thought between the women and Cardinal James Francis McIntyre, who was head of the Archdiocese of Los Angeles until 1970. He took an authoritarian approach to leadership and saw them as a threat to the church community he was building in Los Angeles. If you opposed him, as he saw it, you were opposing the church.

Cardinal McIntyre liked the power and the celebrity of his position. As his secretary put it, “He’s not into theology much. He’s a businessman.” He was a runner on Wall Street before becoming a priest, but as such he was a financial help to the church in Los Angeles. He built schools to the point that it felt a new one opened each week, and they had to be staffed...with sisters.

There were 62 schools and 24,000 students. Cardinal McIntyre was in charge of those schools, and he enlisted his nuns to teach for free. No social security. No pension. No salary. Untrained teachers were put in front of classes of over 80 kids. Most had no college degrees, let alone a teaching credential.

It was defeating for the nuns. As they themselves tell it, the infamous stories about lingering scars—literal or otherwise—from mercurial nuns in Catholic school likely came out of that period.

But while the schools were under Cardinal McIntyre’s rule, the Immaculate Heart College was theirs. The sisters owned it, and they loved it. They were able to be a part of the world, in tune with the issues of the day.

Much of Rebel Hearts centers on the euphoric and combustive time between 1963 and 1970, a time of renegade-tinged love, freedom, flower power, the boom of feminism and the blossoming of bright, ambitious women. That was echoed on the campus of the college. They were encouraged to be experimental, attaining world renown in just about every department, from music to art to publishing. Jane Fonda would pop by.

Cardinal McIntyre did not like any of this. He started censoring the faculty. When a typically vigil-like Mary Day celebration in honor of the Virgin Mother was transformed into a flower-crown wearing, skipping-and-dancing paean to womanhood and revolution, he blew a gasket and threatened to close the college.

There’s important context behind much of this: From 1962 to 1965, it was happening against the backdrop of the Second Vatican Council (aka Vatican II) and larger conversations about church reform and modernization. The women at Immaculate Heart were ecstatic about the changes that came with Vatican II. It gave them a framework for what they already wanted to do when it came to engaging with the community and the church. It also put them in Cardinal McIntyre’s crosshairs.

Part of that meant protest. Patrice Underwood, who was then Sister Patrice, attended the march in Selma alongside Martin Luther King Jr. and Coretta Scott King. Her picture was in the Los Angeles Times, holding hands with one of the Black activists. “It was the first time I was scared of white people,” Underwood remembered. “I was scared to death of the policemen. I was scared to death of every white man who drove a car past us. That’s when I realized this is how these people have to live day after day.”

She had lunch with Coretta King, just the two of them. “She said ‘Martin and I had to make a decision: The cause of justice is more important than the two of us and our own family being safe,’” Underwood remembered. That stuck in her mind. “No matter what may happen, you have to let go. It was hard, but it was a real spiritual awakening about what it really means to care for your neighbor.”

When Cardinal McIntyre saw her name in the LA Times, he called her mother superior and asked who gave her permission to go to Selma.

The sisters at the time were, despite their age, part of a youth movement. The leaders may have taken their vows in the 1940s, but their followers were young nuns filled with the mission-focused spirit of the ’60s. The nuns of the college attended peace marches against the Vietnam War. They demonstrated for farm workers during the grape boycott.

When Sheif is asked if she’s ever been arrested, she responds with a laugh, “Yes. A lot of times.” Then more seriously: “If you really believe that something is wrong, then it is important to put your body on the line.”

But as they talked about the modern world, their own labor issues came up. After Vatican II, an official approach to deal with these issues existed. The sisters complained about their job conditions: Overcrowded classrooms, sleep deprivation, and the lack of training. As one nun said, “Not only are we destroying education, we are destroying sisters.”

They also wanted to do away with the traditional habit in order to adapt to modern life. The habit became a symbol of the constraints and oppression of previous times. People respond to them differently when they wear them. There’s a barrier in the habit. There’s a presumption, intimidation. People don’t talk or behave freely.

In 1967, a general assembly gathered to vote for the changes they demanded: Decent working environments in schools; freedom to regulate prayer life, habits, cultural life; and freedom for individual responsibility in civil and social causes.

After a years-long fight, they were struck down, leading to an almost impossible decision. It wasn’t just whether to fall in agreement with the cardinal or not, or whether to decide to fight for independence or not. It was whether to have vows or not have vows. As Dowling says, “We did take vows: poverty, chastity, and obedience. But there came a point where conscience said we will not be dictated to or shaped by a power that oppresses.”

The story of the Immaculate Heart community is a living, breathing one. It’s no longer defined solely by the schism between the women and the institution of the Catholic Church. It’s colored by their motives for standing up in the first place, and everything they’ve rebelled against since. For 50 years since being presented with that painful choice, the community has thrived secularly as a vehicle for pushing social change.

But what the story of the Rebel Hearts shows is the remarkable tenacity of a few hundred women whose faces were hidden by habits, but whose work reverberated not just through the church, but through society. They unveiled the peril of refusing to change with a changing society. And they’re still doing it. As Dowling says, “A movement is a movement. By definition it keeps going.”