A Changing Heart occurs during the time of Jesus' ministry in Israel. A Pharisee named Joel is an influential leader of the Pharisee Brotherhood in Jerusalem. He seeks to teach his people to follow the strict traditional religious teachings handed down by his Brotherhood for many years to create a utopian society that unconditionally follows God.
Joel has been a teacher and scholar of the Mosaic Law and Prophets. His family has faithfully followed and observed all the teachings of the Pharisee Brotherhood. Joel feels his life has been peaceful and content, and he is fulfilling his passion for teaching God's people. However, when Jesus of Nazareth begins his ministry of salvation, healing, and deliverance, Joel feels threatened. He soon discovers that his family has become hungry for the fellowship and relationship with God that Jesus teaches and demonstrates before large gatherings.

Joel does not understand Jesus. He believes Jesus is a good man who desires the best for the people, but Joel believes Jesus has been confused and misled somewhere. After Joel's wife, Diana, and other family members become interested in Jesus and his teachings, it angers Joel, and temporarily, he becomes involved in a plot to end Jesus' ministry. Joel's final blow comes when his son, Asa, joins the Zealots in their insurrection against Roman authority and is faced with death.

Joel soon learns that he is a broken man and there might be more to Jesus' ministry than he has been willing to admit. He battles his pride and the judgment of others to follow Jesus to his crucifixion and becomes a witness to his suffering and death for humanity. Through Joel's eyes, the Gospel is unfolded and plain to understand.