As the Lenten season of Penance is observed in the Convent of the Daughters of Compassion, Sister Joan finds herself struggling with her less-than-Christian feelings toward two very prickly personalities: the serious and rather stiff Father Timothy and the dour Sister Jerome. Soon, however, she finds herself wrestling with a larger transgression - murder. When the rectory housekeeper is found dead of a pill overdose, Sister Joan refuses to believe the police's suspicions of suicide - and an accident seems equally unlikely. A sudden rash of corpses appears to bear out her theory. Now as she grapples with her conscience and her vows during the holy season, the fearless nun sets a trap for a killer... but she may well find herself caught in an unholy - and deadly - snare.