Philomena, a retired Irish nurse, had given birth to a son out of wedlock when she was a teenager. At the time, Ireland was a strictly Catholic country and unwed mothers were considered sinful and shunned by society. Philomena's father, unable to support his daughter and her son, sent her to live in a convent where the nuns took her son away from her and put him up for adoption without her consent.
Fifty years later, Philomena decides to search for her son and turns to journalist Martin Sixsmith for help. The two set off on a journey to the United States to find out what happened to Philomena's son. Along the way, they uncover a shocking truth about what happened to many unwed mothers and their children who were taken from them by the Catholic Church and sold to American families.
As Philomena and Martin get closer to finding her son, they face obstacles and setbacks that challenge their strength and determination to uncover the truth. Through it all, Philomena remains persistent in her search for her son and determination to find closure after decades of pain and heartbreak.