Julia resides in a quaint, struggling town called Cold Rock in Washington. As the local nurse, she grapples with the haunting memories of her late husband, the town's former doctor. Once a thriving mining community, Cold Rock is now steeped in poverty, with the school closed and the town nearly forgotten. Throughout her days, Julia visits various families, including Jenny and Carol, who endure a tumultuous life with their mother and her cruel, alcoholic boyfriend, who has left Carol expecting. Julia's anger mounts as their mother chooses to keep him around, ultimately forcing Carol and her newborn to leave the home.
Jenny, burdened by her harsh experiences, has become selectively mute, expressing herself through a journal she carries everywhere. She sketches scenes from her life, including local folklore, particularly "the tall man," a mysterious figure associated with the disappearances of children in the area.
Returning to her large home on the outskirts of Cold Rock, Julia shares her life with her son David and his nanny. One fateful evening, after putting David to bed and drifting off on the couch, she is jolted awake by unsettling sounds from downstairs. As tension mounts, she discovers the nanny bound and gagged, and in a panic, finds that David is missing. In a frantic search for what seems to be "The Tall Man," Julia slowly uncovers a shocking truth: David is not her son; he is one of the abducted children. The actual kidnapper is the boy's biological mother, desperately trying to reclaim her child while the town dismisses her claims as mere delusion.
With Jenny's guidance, Julia embarks on a desperate mission to find the mother and retrieve David, leading her into the treacherous tunnels beneath Cold Rock, remnants of the town’s mining past. In an unexpected twist, Jenny pleads with Julia to let The Tall Man take her as well. Initially hesitant, Julia ultimately agrees but implores her to remain silent about it until The Tall Man’s arrival. As tension escalates, law enforcement arrives, and a mob forms against Julia, who faces a grim fate in prison as a perceived child killer. Despite admitting to heinous acts, it later unfolds that her confession was a fabrication; she is part of a covert organization aimed at rescuing children from abusive situations, striving to break the cycle of hardship and neglect.
Meanwhile, Jenny witnesses her mother embroiled in yet another drunken brawl with her boyfriend, prompting her to wander into a nearby field. There, she encounters The Tall Man, revealing the truth: Julia's husband, who was thought to be dead, awaits her. He leads Jenny to a new home and identity with a loving family. The Tall Man, refusing any form of payment, emphasizes the selflessness of Julia's actions for the sake of the children she helps.
As the story unfolds, Cold Rock continues its downward spiral, with Julia imprisoned. The authorities abandon the search for the missing children, convinced they were buried in the perilous tunnels. In stark contrast, Jenny thrives in her new life, blossoming in an environment that nurtures her artistic talents. She begins to vocalize her feelings in a voice-over, expressing gratitude towards her three mothers: her birth mother, who she misses; Julia, for opening the door to a new life; and her new mother, who provides her with love and support. As Jenny strolls through a park, she catches sight of David with his adoptive family, suggesting an ambiguous ending; she feels a pang of longing for her past yet contemplates the societal implications of her new reality, questioning whether it truly signifies a better life.
