General Toda Rai, the Rajput leader of a princely state nestled in the Himalayas, extends an invitation to the Congregation of The Servants of Mary, an Anglican nun order, to set up a school and hospital at Mopu, a dilapidated harem perched high on a cliff. Sister Clodagh, an ambitious nun appointed as Sister Superior, arrives in Mopu accompanied by four other sisters: Sister Philippa, who is responsible for gardening; Sister Briony, in charge of the infirmary; Sister Blanche, affectionately nicknamed Sister Honey, tasked with teaching lace-making; and the emotionally fragile Sister Ruth, assigned to teach English and mathematics.
The local British agent, Mr. Dean, outlines the numerous social and environmental hardships the sisters will likely encounter. He points out that previous attempts by monks to establish a school in the area have failed and predicts that the women will leave as soon as the monsoon season arrives. Thus, it becomes crucial for Sister Clodagh to maintain the well-being of the nuns, especially since the Congregation permits every nun to depart after one year of service.
As the sisters settle in, they find it challenging to integrate with the local community. The native caretaker, Angu Ayah, treats them with disdain. Further complicating matters, the general's wealthy uncle abandons his duties to become a Hindu holy man, spending his days in meditation upon a mountain within the monastery's domain, refusing all communication. The sisters take in Kanchi, a local girl, in an attempt to manage her unpredictable behavior, and they also commence tutoring the general's heir, known as the Young General, in Western customs ahead of his journey to Britain. When Ayah punishes Kanchi for stealing, the Young General intervenes, soon developing feelings for her—a situation that Mr. Dean likens to the classic tale of The King and the Beggar-maid.
However, each member of the convent begins to suffer from ailment and emotional distress caused by their unsettling environment. Sister Clodagh reflects on a past romantic failure that led her to the convent. Sister Ruth becomes envious of Clodagh, while Philippa loses herself in the surrounding landscape, burying herself in flowers instead of vegetables for the garden. Sister Honey’s burgeoning bond with the local children culminates in tragedy when she mistakenly administers the wrong medication to a critically ill infant, resulting in the child's death. This failure incites anger from the locals, who abandon the mission and place additional strain on the sisters. Mr. Dean attempts to persuade Sister Clodagh to leave before further misfortune befalls them.
Moreover, the sisters grapple with their vows of chastity, as the old palace is adorned with suggestive art from its previous era, which continually tempts them. Sister Ruth, already unstable, becomes infatuated with the dashing Mr. Dean and orders an alluring modern dress to entice him. While Sister Clodagh is irritated by Mr. Dean’s indifference, she finds herself inexplicably attracted to him, a feeling she is unwilling to acknowledge. Sister Philippa decides to leave, expressing to Clodagh that “there are only two ways of living in this place. Either you must live like Mr. Dean, or like the holy man. Either ignore it or give yourself up to it.”
In a desperate moment, Ruth informs Clodagh's Reverend Mother of her desire to return to Britain. Clodagh visits Ruth to plead with her to stay, aware of how shorthanded the convent is. Ruth, having changed out of her nun's attire into her modern dress and boldly applying lipstick, indicates her yearning for freedom. She slips away while Clodagh is asleep and goes to Mr. Dean’s residence to declare her love. However, the cynical Mr. Dean spurns her advances. Devastated, Ruth suffers a breakdown and returns to the mission with intentions of harming Clodagh. When Clodagh rings the morning service bell, Ruth makes an attempt to push her over the cliff. Their struggle ends with Ruth falling to her death.
The fatality of Ruth marks a turning point for the Congregation, leading them to shut down the mission and demote Sister Clodagh. The remaining nuns depart just as the monsoon season begins—a departure that occurs even earlier than Mr. Dean had initially predicted. At the caravan, Mr. Dean comes to bid farewell, and Clodagh clasps hands with him, sharing a poignant gaze before she steels herself and moves on. She makes one last request of him (which he wholeheartedly agrees to) to take care of Ruth's grave.
