The priest, Father Merrin, successfully defeats the demon Pazuzu and frees Regan. However, Merrin dies of a heart attack during the exorcism. Regan is left traumatized by the experience, but she eventually goes on to live a normal life.
In the film:
The film ends with the demon being exorcised from Regan, and her returning to normal. However, the priest who performed the exorcism, Father Merrin, dies in the process. The final scene shows Regan's mother holding her in her arms and telling her that everything is going to be okay.