Changeling (2008)

Los Angeles, 1928. A single mother returns from work to find her nine-year-old son gone. She calls the LAPD to initiate a search. Five months later, a boy is found in Illinois who fits the description; he says he's her son. To fanfare and photos, the LAPD reunite mother and son, but she insists he's not her boy. The cops dismiss her as either a liar or hysterical. When she joins a minister in his public criticism of the police, they in turn use government power to silence and intimidate her. Meanwhile, a cop goes to a dilapidated ranch to find a Canadian lad who's without legal status; the youth tells a grisly tale. There's redress for murder; is there redress for abuse of power?