Xavier "Xavi" Lavezares was supposed to be a brilliant psychiatrist with a bright future ahead of him, until his sister Mara killed herself in front of him in the throes of a supposed demonic possession. Trying to find answers in a vocation he thought he'd never take up, Xavi becomes a man of the cloth who spends his spare time taking apart cases for exorcism. After the Vatican calls for an increase in the number of exorcists worldwide, Fr. Xavi is tapped to become to an exorcist. But when a botched exorcism ends in murder and leaves a supernatural echo from the trauma of his past, he enters a downward spiral as he is forced to confront the possibility of a reality far greater than his own. When idealistic young clairvoyant Sister Barbara "Barbie" Vergel de Dios finds one of her former students experiencing the symptoms of possession, she is convinced that it is real. But she has trouble finding an exorcist to believe her. When Fr. Xavi is put on the case as a last resort, she sees one last chance to find help for the girl. With the aid of his keen observation skills, his rigorous learning, a heady clairvoyant assistant and perhaps a little faith, the cynical Fr. Xavi must find the means to confront a gripping darkness bigger than himself, and in doing so find some measure of purpose and redemption.