Cory Wardell is not a very nice young man. He is in a maximum security prison after being convicted of serial rape where he gave his victims (all virgins)the choice of being raped or being murdered.
Father Jacob is called to the prison by the prison chaplain, Father Daniel, (David Guyasi) when Cory begins to show signs of being possessed by none other than Saint Maria Goretti, a young girl who, when attacked, chosen death rather than rape and was stabbed fourteen times. Like Wardell, Maria Goretti's attacker gave her the options and Wardell, it seems, called all of his victims 'Maria' when he was attacking them. When Father Jacob visits, Wardell begins sweating blood and then speaks in the voice of a young girl but Father Jacob is not convinced and he and Father Daniel spend the night in Wardell's cell where Father Daniel is visited by an erotic apparition and Father Jacob believes that while something is definitely wrong, there has never been a known case of saintly possession.
Looking into Wardell's past, Father Jacob discovers that one possible victim of his has never been found and she is presumed dead. When Father Daniel identifies the girl from his dream on a Missing Person's photograph, Father Jacob realises that it is the spirit of the dead girl and not Maria Goretti who is possessing Wardell. When Wardell escapes from prison, he is found at the home of the missing girl where her mother is holding a knife to his throat and hysterically demanding that he tells her where she can find her daughter's body. Father Jacob speaks to the spirit of the girl and Wardell dicloses the location of the body which is in almost pristine condition.
Another excellent episode which is par for the course for this terrific series.