Dirty and wild, Darlin', a 16-year-old girl, finds herself taken to St. Thaddeus Hospital after an ambulance accident. Within the hospital's walls, Tony, a compassionate nurse, develops a bond with her, which clashes with the stern approach of the hospital's doctor regarding Darlin's peculiar condition. Outside, The Woman, lurking with a sinister intent, is determined to connect with Darlin at any cost.
In a shocking twist, The Woman brutally kills a homeless man named Charlie, slicing off a piece of flesh from his body to tempt Darlin with food through her hospital window. Disturbed and rejecting her surrogate mother, Darlin shuts her blinds on The Woman. Meanwhile, the ambitious Bishop, aiming to save St. Philomena's Catholic school from closure, devises a plan to use Darlin to create a publicity boost for the school, going so far as to blackmail Sister Jennifer into manipulating Darlin's behavior.
At St. Philomena's, Darlin encounters a group of other orphaned girls, including the quirky Billy and the hostile Bug. The Bishop and Sister Jennifer resort to extreme measures, locking Darlin in an animal pen while filming the ordeal to document her supposed "rehabilitation." Following this encounter, Darlin reminisces about a fleeting moment with a boy she once kissed.
As chaos unfolds, The Woman stalks the hospital corridors, clearly searching for Darlin, eventually discovering her empty bed. In the chaos, The Woman bites a police officer who makes the mistake of treating her as a mere vagrant and steals his gun. She later penetrates the hospital's defenses, leading to a bloody confrontation that results in several deaths, including that of Darlin’s doctor.
Through a series of events, Darlin begins to connect with Billy, who bravely helps her navigate the woods surrounding the school. However, trouble brews as Tony, now caught between the two women, finds himself at the mercy of The Woman, whose rage leads to a car crash during a police chase. Meanwhile, The Woman takes refuge in a camp of homeless women led by the intriguing Mona.
As Darlin adjusts to life at St. Philomena's, Sister Jennifer starts finding ways to reach her, introducing simple joys such as blowing bubbles and gifting her a doll-shaped cookie, which brings a glimmer of happiness to Darlin's troubled life. Yet, the shadows of her past linger—her connection to The Woman grows more potent.
Revelations about Darlin's pregnancy shake the school to its core, leading to divine rituals and a baptism orchestrated by the Bishop. As tensions rise and Darlin's psychological turmoil grows, she finds herself in a nightmare painted by her traumatic experiences, particularly questioning the dark figure that seems to lurk within her.
In a gripping climax, the Bishop’s dark motives are exposed publicly, triggering a chaotic confrontation as The Woman storms St. Philomena's with a vengeful force, intent on reclaiming Darlin. Amidst the chaos, Darlin goes into labor, forcing the two women to confront their bond amidst bloodshed and chaos.
In the end, Darlin's pleas for escape from her painful lessons lead to a heartbreaking decision. As The Woman departs with Darlin’s newborn, Darlin is left behind in her tumultuous world, comforted by her new friends, with sirens blaring in the distance, heralding a new chapter fraught with uncertainty.
