In “A Rare Benedictine,” Ellis Peters proves herself just as adept at short, self-contained mystery stories as in her novels. There are three here, all fascinating. Her characterizations, short, even terse, but eloquent, are half the fun. Like an expert portraitist, the author paints detailed, intricate and intriguing human images with a minimum of bold strokes. Much is seen through the perceptive and restrained vision of Brother Cadfael, in equal measures man of the world, man of the people, and man of God.