Changeling (2008) on Netflix

In March 1928 in Los Angeles, Christine Collins lives with her beloved son Walter in Lincoln Heights. When she is assigned to work overtime on Saturday at Pacific Telephone and Telegraph as supervisor, she promises Walter she will return at 4PM to watch the latest Charles Chaplin movie at the movie theater with him. However, she arrives home late and does not find her son; after seeking out the boy in the neighborhood, she reports the missing child to the police, but the police officer tells that she should wait twenty-four hours to register the complaint. Five months later, Captain J.J. Jones communicates to Mrs. Collins that her son had been found in DeKalb, Illinois, and is heading back home by train to be reunited with her. In the train station, Christine does not recognize the boy as being Walter, but Captain Jones advises her that his appearance has changed during the five months. Soon she confirms that the boy is not her son, but the corrupt LAPD does not accept her arguments. When Mrs. Collins is approached by St. Paul Presbyterian Church Pastor Gustav Briegleb, who daily broadcasts protests exposing corruption in the police force, she decides to disclose to the press the evidence she has about the changeling. However, the abusive Captain Jones sends Christine to an asylum to intimidate her. Meanwhile the efficient Detective Lester Ybarra is assigned to arrest and deport an illegal Canadian boy who is hidden on a ranch in Wineville. He captures the boy, who discloses hideous crimes committed by his compatriot Gordon Northcott.