Leo is called in by his old college friend,psychiatrist Sean Delaney,now a cancer-stricken alcoholic. Sean was treating inspirational,deeply religious teenager Eve Gilston,who felt neglected by her family ,and the verdict of whose death,alone in bed,apparently of arrhythmic death syndrome Sean does not believe. Accompanied by down-to-earth sergeant Brooks Leo interviews Eve's parents,lapsed Catholics Beth and Tony,wondering if the family is prone to the rare heart condition Long QT Syndrome,though John,their blind younger son refuses to be tested. Sean tells Leo that,at their last session, Eve believed that she was possessed by evil and soon afterwards Leo and sergeant Brooks find evidence that a priest performed an exorcism on her.

Shocked by the news of the exorcism Sean joins Leo in visiting Father Jacobs though he tells them that he did not perform the exorcism and Nikki tracks down the nun,Sister Landsley,who did so,only to find she has killed herself. Leo believes the trauma of the exorcism triggered Eve's death but then he learns from Beth how Eve thought that she was possessed after passing on the measles which blinded him to John when they were younger. With the knowledge that his grandmother killed herself John believes that possession runs in the family and now he is host to the demons, leading to a further exorcism.