When she's at her best as she is here, nobody else comes within kissing distance of Miss Berckman in a form with so many delimiting tags, e.g.--""modern gothic"" -- ""romantic suspense."" The fourth man, an invisible presence, is the equivalent of the breaking point -- reached not too much later in this story of Alison, young casualty of a bad marriage, who takes a job working in the archives of a private library, run by attractive Tom Durant, and living in a small boarding house. Among the other paying guests are Myra, a predatory and prying woman she had known earlier, and very elderly Mrs. Lees-Milburn with a rare collection of old literary letters. The interest swings between Tom, the break-up of his marriage and his possible availability to Alison, and the worth of the letters to ? It's all written up, not down, with supple ease.