Jolie, who puts her wide eyes to tearful use as the desperate mother in 1920s America, is told by the police that they have found her son, and despite maternal feelings and objective facts which tell her that they are wrong, she is forced to accept him by official pressure. When she puts up a fight and proclaims the truth, the snakelike police captain has her thrown into an asylum.
Now, this may seem about as far from the wild west as one can get - Angelina Jolie's character wouldn't have lasted a minute at the OK Corral - but the theme of an individual fighting against the oppression of the state is the same liberal spirit that animates most westerns. The rugged cowboy trying to overcome the corruption of the brutal sherriff and liberate the people from fear is a trope second to none, and one which applies equally here.
It is Jolie's heroic resistance which gives Changeling its spirit, but it does not take much to see Eastwood behind the camera.