Black, who writes historical romances under another name, tries her hand, with considerable success, in the mystery genre. Sister Joan, a nun in the Order of the Daughters of Compassion, is asked by her Prioress, the Reverend Mother Agnes, to move to the Cornwall branch of the order. Mother Agnes is troubled by a letter from aged, recently deceased Mother Frances of the Cornwall convent--a letter that was full of deliberate errors and seemed to her an oblique call for help. Sister Joan agrees to the transfer and, with beautiful young novitiate Veronica Sterling, travels to Cornwall House. Its prioress is Reverend Mother Ann--a regal, worldly woman whose enameled nails and lavender scent give Sister Joan her first confirmation that things are not as they should be in Cornwall. As she assumes her teaching duties at a tiny local school and begins to sort out the members of the order, Sister Anne sees and hears much to perplex and worry her: the death some time before of young Sister Sophia--officially an accident but called suicide by one of the nuns close to her; the abrupt, unexplained departure of novitiate Brenda Williams, whose one-time boyfriend Johnny Russell has come looking for her; and much, much more. Sister Joan struggles with conscience, common sense, and fear, eventually uncovering the subtle underpinning of a misbegotten conspiracy. The intriguing rote and ritual of a cloistered religious community, a firmly crafted puzzle, and a lively, likable heroine --all combine for a fine debut for this first of a promised series.