Martin Sixsmith is a journalist who recently lost his government advisory role in a very public and humiliating fashion. He seeks out a new project, batting around the idea of a Russian history book, despite the fact no one is interested in Russian history. A young woman working at a party approaches him to write about her mother, Philomena. Philomena got pregnant at a very young age and was sent to live in an Irish abbey, where the nuns make her work on their laundry as both a means of earning her keep and as penance for her sins. One day, she finds that her young baby son was adopted by an American couple, despite her getting no warning and no say in this decision. Upon leaving the abbey, they refused to give her any information regarding her son's whereabouts. Sixsmith decides to help Philomena do the research necessary to find her child. When the church continues to deny they know where the child is, Sixsmith finds himself astonished by Philomena's devout religious ways. Their journey ultimately leads them to America, where Sixsmith finds out the truth about Philomena's son. The many details that bubble to the surface shock Sixsmith and Philomena.