A Vow of Silence is by Veronica Black. The first of the Sister Joan Mysteries. When Sister Joan is transferred to a lonely Cornwall convent she discovers the sisters there are keeping secrets. Secrets that include one missing novice, one dead nun, and some very different beliefs. She begins to notice even more departures from normal convent routine and begins to suspect something terrible may be going on in Cornwall.
Ratings: 11th grade - 8 out of 10 - P (profanity) - AC (mature thematic content).