The movie is set in Los Angeles in the 1920s and tells the story of Christine Collins (played by Angelina Jolie), a single mother whose nine-year-old son, Walter, goes missing. Desperate to find her son, Christine turns to the Los Angeles Police Department for help.
However, the police, eager to close the case quickly, present Christine with a boy they claim is Walter after several months. Despite Christine's insistence that the boy is not her son, the police coerce her into accepting him.
As Christine continues to fight for the truth, she uncovers a disturbing web of corruption and abuse within the LAPD. She learns that the police have been abducting children and passing them off as lost or runaway youngsters to meet their quotas and maintain a high clearance rate. Christine's relentless pursuit of justice, which draws support from a sympathetic doctor and a reverend, exposes the department's misconduct and leads to reforms.
Eventually, through the efforts of a private investigator hired by Christine, the real Walter is discovered living just a few blocks away from Christine's home. It turns out that he had been kidnapped by a serial killer named Gordon Northcott, who kept him captive and abused him, along with other children. Walter is rescued, and the truth about the LAPD's actions comes to light.
"Changeling" is a powerful drama that combines elements of crime, mystery, and social commentary.