In the year 1952, in Christchurch, a well-off 13-year-old English girl named Juliet Hulme finds herself transferring to a new school where she forms a close bond with a 14-year-old girl from a working-class background, Pauline Parker. Their friendship blossoms over shared experiences of trauma from childhood illnesses and lengthy stays in hospitals. Pauline is enchanted by Juliet's boldness and stunning beauty, contrasting sharply with her own turbulent relationship with her mother, Honora, marked by constant conflict.
Juliet's home life is intellectually serene, a stark contrast to the chaos Pauline faces daily. As their bond strengthens, Pauline often seeks refuge at the Hulmes’ residence, where she feels a sense of belonging. Together, they indulge in creative pursuits such as painting, crafting figurines, and weaving fantastical stories, ultimately leading to the creation of an imaginary kingdom they call Borovnia. This world becomes the backdrop of the adventure novels they aspire to publish and adapt into films in Hollywood, blurring the lines between their imagination and reality.
Juliet introduces Pauline to the concept of the “Fourth World,” a paradise absent of Christianity, where art and music reign supreme. She believes that after her death, she will ascend to this idyllic realm. On a day trip to Port Levy, when Juliet's parents announce their impending trip, she is overcome with dread at the thought of isolation. In her turmoil, she experiences the Fourth World for the first time, a place where she feels entirely safe and content. Upon sharing this vision with Pauline, they both become captivated by the beauty of this shared experience, deepening their connection.
However, things take a darker turn when Juliet contracts tuberculosis and is sent to a clinic. Despite the physical distance, the girls continue to write to one another, adopting the personas of royal figures in Borovnia. During this time, Pauline becomes involved with a lodger, igniting Juliet's feelings of jealousy. Their once innocent fantasy escapism gradually shifts towards violent imaginings, fueled by the oppression they feel in the real world.
As tensions rise, especially with Juliet’s father expressing concerns about the intensity of their friendship, their world starts to crumble. In response to Juliet's deteriorating family situation, including her parents' decision to divorce and their plan to relocate, the girls concoct desperate plans to escape. Their fantasies spiral into conversations about murder, viewing Pauline's mother as the main barrier to their bond.
In a dramatic climax, the girls spend the final weeks of their friendship together at Juliet's house. When mommy Honora organizes a trip to Victoria Park, the plan solidifies in their minds. After enjoying tea, the family takes a walk, and as Honora bends down to retrieve a pink charm the girls have intentionally dropped, the unimaginable occurs — Juliet and Pauline strike her down with a brick hidden in a stocking.
A haunting epilogue reveals that soon after this shocking act, both girls are captured, sentenced to five years in prison, having evaded death due to their youth, and ultimately released in 1959 with the stipulation that they must never see each other again. Their story is a chilling tale of love, delusion, and the tragic consequences of overwhelming passion.
