The film opens with a wash of fluid, forest, and shadowed hallways as a six-year-old named Iris is discovered inside a coffin placed in a dormitory’s common area. She is welcomed by six girls who share the house, dressed in a uniform that mirrors Iris’s own, while their hair is braided and ribbons are exchanged. Each ribbon marks a girl’s age and year at the school, and Iris instantly becomes the new, youngest holder of the red ribbon. This moment stirs tension with Selma, the former red ribbon who has become the orange ribbon and resents Iris’s arrival, especially since she laments the absence of Natashka, the oldest girl who wore a violet ribbon and is no longer present.
A seasoned violet ribbon, Bianca, quickly steps in to take Iris under her wing. Iris initially feels homesick and longs to see her brother, but Bianca bluntly explains that there is no possibility of that happening here: this is a place where boys are not admitted. The girls take to the water together, swimming in a lake that seems to separate them from the outside world, and Iris befriends Laura, who bears the red ribbon of another house and who grows increasingly withdrawn as time passes. Yet Iris’s new ally is not the only complexity in the school: that night, Bianca slips away on an authorized, enigmatic errand that Iris cannot discuss or reveal.
Daily life at the school unfolds with dance, study, and care routines. Iris attends lessons in a curriculum overseen by two bright young women—Mademoiselle Edith, who walks with a cane, and Mademoiselle Eva, who teaches dance—while each house is tended to by elderly servants whose whispered past suggests they are girls who once attempted to escape the confines of the walls and were punished by being kept on permanently. The story hints at a hidden hierarchy and a history of rules that extend far beyond the classroom.
One night Iris trails Bianca on her secret pass, but the older girl vanishes into the maze-like main building. Iris ventures onward and stumbles into glimpses she cannot parse: a shadowy man preparing an injection for a shadowy woman, possibly one of the elderly servants. Terror and confusion drive Iris back into the woods where she spends the night, unsettled by what she has glimpsed.
Shelter from fear comes in the form of friendship, albeit rough and uncertain. Selma’s hostility gives way to a fragile, complicated bond, but Selma’s cruelty reappears when Iris asks about Bianca’s night outings. She uses a switch to beat Iris and, in a chilling moment, touches Iris’s wound with her fingertip, tasting Iris’s blood. Laura, meanwhile, clings to sorrow and becomes increasingly unable to adapt to life at the school. With Iris’s help—and a pledge of secrecy—Laura attempts a dangerous escape by stealing a rowboat. The plan sinks when the boat leaks and the weather turns foul, and Laura drowns. Iris reveals the tragedy to Bianca, and the school mourns Laura with a funeral and a pyre that burns her coffin.
As winter settles in, the focus shifts to Alice, a ten-year-old who holds the blue ribbon and longs to leave the school to see the world beyond. She eagerly anticipates the annual inspection that will determine which girl may depart with the headmistress, a mysterious figure who arrives from afar to observe. After watching many performances, the headmistress selects one girl, and, though Edith cautions Alice not to count on her, the moment arrives with tense expectation. In the end, another girl is chosen, and Alice is left devastated: she collapses at the headmistress’s feet, stops speaking, and stares blankly into space. Eventually she bolts into the surrounding woods, climbing the stone wall that guards the school. The scene fades on distant gunshots and barking dogs, and Eva later explains that Alice cannot be found, adding that Alice has been deemed “very bad” and will not be spoken of again.
With Alice out of the narrative, Bianca becomes the next central figure. The violet ribbons are instructed about the bodily changes they will soon undergo, and Bianca decides to bring Nadja, the indigo-ribbon girl a year younger, on a nighttime excursion to the main building. Behind a grandfather clock they discover a secret passage and slip into a hidden world of butterfly costumes and clandestine performances. Each night, the girls perform a dance for a mysterious audience; Nadja falters at times, but a man in the audience praises Bianca as the most beautiful and throws her a rose as a token. After the show, Bianca and another girl explore the theater’s deserted spaces and uncover a man’s counting receipts—an unsettling reminder of how the school profits from its secrecy. Bianca treasures the rose and a stray theater glove before casting both into the lake.
The next morning Iris and Bianca share one last day together before Bianca’s departure. Bianca passes her duties to Nadja and, with the violet ribbons, places their ribbons in a box before joining Eva and Edith in a corridor behind the clock that leads to their exit. They board a subway train and leave the school behind. Eva and Edith step away with the girls to begin a new chapter as they reach a grand plaza, where Bianca and the others begin to play in nearby fountains. A group of teenage boys playfully lose a ball in the fountain, and a boy wades in, catching Bianca’s eye as he becomes momentarily obscured by the water’s shimmer. Bianca’s curiosity and joy surface as she splashes back, exchanging glances and laughter with the stranger before the scene fades. The film returns to its opening image, closing on a final rush of water that signals a new, uncertain freedom for the girls who have lived within those walls.
