On March 9, 1928, Christine Collins begins her day with her son, Walter, playfully measuring his height against the wall as she prepares him for school. After a lighthearted farewell at the cable car stop, where Walter shares that he got into a fight after another child claimed his father hated him, Christine reassures him that his father was simply overwhelmed by the responsibilities of parenthood and left before he could build that bond. However, after Christine goes to work as a supervising phone operator for a telephone company in Los Angeles, the joyous routine turns tragic when Walter mysteriously disappears.
Despite initially receiving minimal help from the police, led by Captain J.J. Jones, and Detective Lester Ybarra, she takes matters into her own hands, calling other cities in desperation as they search for Walter. As time ticks on, a new challenge emerges: a boy appears in the news claiming to be Walter. Caught in a whirlwind of media attention, Christine's hope peaks until she finds glaring inconsistencies that suggest this child, although given to her as a police recovery, is not her son. The misidentified child, who eventually turns out to be Arthur Hutchins, does not mimic Walter's mannerisms and exhibits physical differences that trigger Christine's maternal instincts.
When Christine insists the boy isn't her son, she faces mounting pressure from the police, including the dismissive treatment by Captain Jones. After vehemently defending her stance, she’s left with no choice but to fight back against a corrupt and uncaring system that threatens to label her as unstable. Fighting against the institution, she courageously speaks out, gathering evidence and support from allies like Rev. Gustav Briegleb, seeking justice for the injustices faced by missing children.
As the investigation unfolds with chilling discoveries relating to her real son, Christine’s battle turns her life upside down, driving her into an asylum as she fights against being deemed insane for refusing to accept the false narrative imposed by the police. In a harrowing twist, she learns about the existence of other boys and a grim fate awaiting them, leading her to uncover deeper truths that will force the authorities to respond to the severity of their incompetency.
Eventually, against a backdrop of trials, accusations, and heartbreaking revelations regarding Northcott's heinous crimes, Christine emerges not just as a mother on the hunt for her child but as a symbol of resilience, courageously standing against the systemic neglect of the institution. While the relentless search for Walter Collins ends tragically, Christine gains something more profound from her fight: hope. Always hoping for a brighter tomorrow, believing that perhaps Walter survived, living in secret, waiting for the day he could reunite with her, and reaffirming that the bond between a mother and her child can never truly be severed.
