There is something of Anne Douglas Sedgwick -- something of ""Elizabeth"" -- in Ann Bridge. She is writing with more assurance, more finesse. And she is, perhaps, most successful when tracing the emotions and motives of women at middle age. Unlike her heroine in Illyrian Spring, this woman is only too aptly compared to the plant, Enchanter's Nightshade, which gives the book its sinister name. But she is skillfully drawn, and brought up by contrast with the sharp but basically kindly old grandmother, the innocent young daughter, the naive English governess thrust into their midst, ill-prepared to cope with the intricacies of Italian life. A glamorous background -- country house life in southern Italy -- and a plot that just avoids becoming melodramatic. Ann Bridge is good property. She fits the demands of the more selective rental customers; and is sound buy as well. Substantial publisher backing.