Murder and the Faith Healer

Can faith be a weapon that is used against the believer? Someone is trying to kill the heiress of an estate or use her faith to have her declared unfit to manage her affairs. The detectives must discover who is trying to harm her. Are the threats against her coming from outside the house or from someone who is living in stealth within its walls? Are those who stand closest to a target the ones who are most likely to strike it?