Murder in Black and White

"She was poisoned."

Such is the cryptic note the archbishop receives after the funeral of Mother Rose. The nuns believe she died of natural causes and the archbishop sends Father Andrew Nolan-Andy-to identify the killer and then participate in a cover-up to protect the Church from scandal. Andy succumbs to the assignment only because if he refuses, his request for a dispensation from the priesthood to legally marry Mia (with whom he has been having an illicit affair) will be denied.

¿How will Father Nolan find a killer whose poison leaves no trace in the human system? How will he guide the nuns in their spirituality when he's secretly spying for the archbishop?