A Vow of Devotion

Sister Joan, that robust, cheerful English nun, makes her sixth appealing appearance (following A Vow of Penance). Assisted by unbelieving Det. Sgt. Alan Mill, Sister Joan, 38, fights the evil that has entered the Cornwell convent of the dedicated Daughters of Compassion along with two postulants-the latter a rarity these days. Joan sees a batlike shadow on the convent walls the night the would-be nuns arrive, and finds expensive hothouse roses left in odd places. One of the candidates is strange, frightened Magdalen Cole of London, of whom Joan harbors an un-nunlike distrust-especially after the nun who changed beds with Magdalen is murdered. The other candidate is sunny, eager Bernadette Fawkes of Yorkshire. Arriving in the area at the same time is a large group of New Age travelers, whom the generous Joan supposes to be ``rather like'' Jesus and his disciples ``journeying about the Holy Land.'' Because the mystery here is fairly straightforward, readers will find most satisfaction in Black's rendering of convent life and in the charms of Sister Joan's earthy good sense. (July)