After taking vows in the 1960s/1970s the nun who would become Reverend Mother was friends with Father Maurice, a priest who had been ordained at about the same time. With their ideas the term radical was applied to her and Maurice.
Sometime before the early 90s she was elected the abbess of the convent attached to St. Katherine's Church in San Francisco. By then the neighborhood where they were located was in serious decline, with hardly anyone showing up for Mass and the convent about to close due to funding problems. The choir was not performing well, barely able to keep a tune and poorly organized.
When Reno lounge singer Deloris Van Cartier witnessed a murder by her lover Vince LaRocca Lt. Eddie Souther of the Reno police department made arrangements for Deloris to stay in the convent. Reverend Mother was less than pleased about the arrangement, fearing the convent would be in danger. The pastor Msgr. O'Hara assured her that law enforcement would protect the convent and the Reno police department would make a generous donation to the convent. When they went into her office Reverend Mother excused herself and told O'Hara she couldn't possibly do this, but O'Hara reminded her of her vows to take strangers needing help in.
Reverend Mother completed Deloris's disguise by giving her the name Mary Clarence and dressing her in a habit. Over the next few weeks Deloris struggled to fit in to convent life, including waking up at 5:00am, sharing simple meals with others, and following the rules Reverend Mother laid down. She did make friends with a number of the nuns there, including Sister Mary Robert, Mary Patrick, and Mary Lazarus. After discovering Deloris had taken a late night trip to a bar she ordered that Deloris would only sleep and sing for the rest of her time there.
Soon after arriving at choir practice the nuns realized just how strong Deloris's music background was. Mary Lazarus stepped aside, and Deloris became the new leader of the choir. The following weekend the choir performed for the first time under Deloris, showing marked improvement as they sung Hail Holy Queen. Upon finishing the hymn in the traditional manner the choir broke out into a rock and roll inspired retelling of the hymn. Hearing this music people began coming in off the street, including young teenagers.
Reverend Mother was not happy to say the least, and severely chastised Deloris for that performance. She was about to have Mary Lazarus resume leadership of the choir, but Msgr. O'Hara intervened, saying that the music was heavenly, and more importantly it brought people in to the church. Deloris talked him into letting the nuns go out in to the neighborhood to fix things up, telling O'Hara it was the Reverend Mother's idea.
With the nuns out engaging the neighborhood instead of hiding away there was a drastic improvement in the area. Soon the church was filled to capacity on the weekends, with the money finally becoming available to repair the roof. The Reverend Mother however felt that time was starting to pass her by and that maybe it was time for her to leave. Upon learning that the Pope John Paul II was going to visit the church to see the choir perform she asked for a program of traditional music be performed. However the choir decided that they would let Deloris pick the music. At that the Reverend Mother made up her mind to resign and move elsewhere.
Vince discovered where Deloris was hiding he had her kidnapped by Joey and Willie. They returned her to Reno so that Vince could confront her before having her killed. Reverend Mother told the nuns the truth. The woman who brought the convent back to life was not a nun, her real name was Deloris, and she was hiding in the convent to keep safe from the men who had just kidnapped her. Even with the truth known the nuns begged the Reverend Mother that didn't often see eye to eye about matters to go rescue their friend. The Reverend Mother and the other nuns of the convent went to rescue her.
Deloris managed to escape when Vince left Joey and Willie to kill her. As she ran through the casino she was reunited with the nuns. Cornered in a room by Vince, they were saved when Lt. Souther shot Vince in the arm.
The two women came out of the experience as friends. With Vince being carted off to jail with fresh new charges waiting for him in addition to the previous murder charge Deloris no longer had a reason to hide. Her zest for life reawakened, the Reverend Mother decided to stay and continue the work Deloris had started. They returned to San Francisco where the choir performed for Pope, who was quite pleased with the work the choir had done. In the months after the choir had several very well received singing engagements under the direction of Deloris.
Sister Act 2: Back in the Habit
Eventually Deloris resumed her solo career, performing a musical act in Vegas based on her experiences in the convent. The nuns went to work for St. Francis Academy, the same school where Deloris had been educated as a child. Learning that the school was in danger of closing Reverend Mother sent Mary Patrick, Mary Robert, and Mary Lazarus to go visit Deloris and relay the Reverend Mother's request for assistance. Deloris agreed and came back to San Francisco, where the Reverend Mother brought her up to speed on the situation. She sought for Deloris to teach the school's music class, due to both her talent for music and the fact that she felt Deloris could be a good role model for the rough and unruly inner- city students there, showing them how someone can come from bad backgrounds and have bad habits yet still turn their lives around and do great things.
Resuming her Mary Clarence persona, Deloris taught the music class at the school. She was able to bring about a change in the students, who had been rude and unruly. The principal Father Maurice was uneasy about Deloris and her unconventional methods, but the Reverend Mother gently reminded him that they too had once been seen as radicals in their younger days.
Getting them interested in learning and singing, Deloris was able to bring them to perform at an all-state choir championship, and raised the funds to do so. For the first time in many years the school won the championship. Seeing the many positive changes the Diocese decided to keep the school open.