Sent to a convent because she had become pregnant out of wedlock, Philomena was kept a virtual working slave while her son was readied to be sold to willing parents. Watching her son being taken away all but broke Philomena.
When she learns her son was taken to the United States she wants to try to find him just to see if he remembers her or anything about his Irish ancestry.
The doors keep closing and it is only the dogged journalistic skills of Sixsmith that manages to uncover the truth.