Self-styled junior shrinks may enjoy trying to crack this slick psychological whodunit in which teenaged Sarah Carpenter, the ""only child of talented, upper middle class parents,"" is plagued by a recurrent dream of murdering her mother. The nightmare, set by a tiny grave overlooking water, is always followed by a ritualistic theft of something small and inexpensive--colorful scarves, costume jewelry, etc. But what do these cheap baubles have to do with Sarah's classy, understated supermom? Can Mrs. Carpenter really be the victim of Sarah's homicidal fantasies? Or does Sarah actually have it in for her mysterious Aunt Katrin, a nomadic artist who's suddenly popped up at the Carpenter's townhouse after lo, these many years and who, by not-so-strange coincidence, always liked ""gypsy"" outfits with colorful scarves, costume jewelry. . . . The expected unmasking of Aunt Katrin as Sarah's real mother--abusive ""MommyKat""--requires the help of an ultrabrainy Briarcliff classmate, visits to a clairvoyant and the New York Historical Society (to pinpoint the real-life locale of the dream), and finally a trip to Riverside Park where by a tiny child's grave Sarah is shocked into remembering the traumatic day MommyKat abandoned her. The pieces of this improbable puzzle fall together far too easily and fit together much too tidily. Still the sleuthing around Sarah's subconscious is diverting enough and Anderson's glib delivery, like Sarah's glamorous lifestyle, is easy to take.