In the shadowed Finnish forest, Saga and Jon venture into a derelict house that once belonged to Saga’s late grandmother, a place steeped in memory and quiet foreboding. They discover a tree forcing its way through the floorboards of the bedroom [Saga] shared with her sister, Taru, a sight that feels almost sacred and terrifying all at once. Jon envisions rejuvenating the ruin into a warm family home where they can raise children together, a plan that promises continuity and belonging. Into the surrounding woods they go, and Saga reaches out to a tree whose trunk resembles a pregnant belly, a primal image that lingers as they share an intimate moment amidst the trees. The moment is charged with both tenderness and unease, as if the forest itself is listening.
Saga’s childbirth proves devastatingly difficult, tearing her birth canal in a way that unsettles everyone present, and the infant—a baby boy—emerges disturbingly silent. On the maternity ward, the infant’s cries come only when the curtains are drawn back, a haunting sign of something not right. Breastfeeding leaves Saga’s breasts bloodied and swollen, and the baby’s skin is thick with dark, almost hairlike growth. The newly renovated house soon hosts a nursery where Saga’s childhood bedroom now sits, a stark shift from the girlhood of years past.
During a visit from Saga’s mother, Saga's mother and Taru, Saga voices a growing fear that something is deeply wrong with the baby, calling him only “it” as if naming him could banish the unease. Her mother remains practical, brushing aside the concerns even after the infant violently tears a piece from Saga’s earlobe, a jolt that unsettles the already strained nerves of everyone in the house. A naming ceremony in the garden unsettles the guests further; the baby’s appearance and his stark, visceral cries unsettle the crowd, while a gust of wind from the forest sweeps a cover over the stroller, shielding him from the sun’s light. Saga declares the baby will be named Kuura, a choice that stings Jon, who had hoped to name him Christian after his father. As the sun retreats, the light leaves dark burns on Kuura’s skin, a troubling omen.
Kuura’s behavior grows increasingly strange. One night, Saga falls asleep while trying to soothe him, and when she wakes, she finds he has slipped from his cot and is transfixed by the tree that has begun to push through the nursery floor again. The next morning, Jon discovers the floorboards ripped apart and Saga sleeping among the tree’s roots, cradling Kuura. A cut on Saga’s hand reveals Kuura feeding on her blood, an act that chills her but also signals a disturbing bond forming between mother and child. At a local clinic, a clinician brushes off Saga’s worries, insisting Kuura is simply advanced for his age and recommending counselling to help her bond with him. In defiance, Saga begins secretly feeding Kuura blood instead of milk, a decision she keeps hidden from Jon.
Meanwhile, Taru recounts the grandmother’s warnings about the forest’s dangers, mentioning that she kept scrap metal around because “cold iron bursts them.” The property’s menacing atmosphere deepens as Jon’s parents visit; his father—John Thomson—blesses Kuura with holy water, an act that has no physical effect on the child, yet the sense of ritual clashes with the growing sense that something elemental and dangerous resides within the boy. Later, when Kuura grasps an unused, cold iron, his hand is severely burned, a cruel coincidence that fuses the supernatural with the mundane in the family’s eyes.
Tensions between Saga and Jon escalate as he worries that Saga is not socializing Kuura properly or seeking the help the clinician suggested. He discovers she hasn’t pursued the referral, and a fierce argument pushes him to leave the house with Kuura, a move that triggers a violent confrontation. Saga awakes to find Kuura’s grip on her, and she locks herself in the bathroom while he tries to breach the door, threatening to end them both. She calls her mother in a panic, admitting a fear that she might need to kill Kuura to protect herself, though her mother insists there is nothing extraordinary at play.
An overnight trip to the city only widens the rift; separated from her son, Saga develops a painful rash that only fades when she hurries back to the house. Kuura’s violence intensifies as a visit from Taru brings Anna, and Kuura bites off Anna’s finger. Jon attempts to feed Kuura ordinary baby food, but the boy rejects it, hurling a jar at him, and Saga begins feeding him raw meat instead. Jon accuses Saga of turning Kuura into a monster, and a desperate, physical struggle erupts when he tries to take Kuura outside the house. Branches erupt through the nursery floor and windows during the clash, fatally impaling Jon through the chest, a brutal, almost inevitable moment in a conflict that has simmered for months. Saga and Kuura, driven by something primal, feed on Jon’s blood and heart, sealing a chilling, intimate bond between mother and son in the wake of tragedy.
In the final, unsettling image, Kuura runs into the garden as a humanoid figure separates itself from one of the trees and approaches with outstretched arms. Saga watches from the porch, a wry, uncertain smile crossing her face as Kuura giggles and returns the smile, suggesting a future that is inseparable from the forest’s reach and the family’s darkest secrets.
