Death Came Smiling — Eileen Dewhurst

'The only difference between me and other people,' said Gwen, 'is that I carry my sanity separately. It lives in the country, and paints, and suffers fools.' When Gwen goes to the country to visit her beloved twin sister, Elizabeth, she is found stabbed in the family home. The open verdict leaves their mentally deficient brother under suspicion, but Elizabeth refuses to accept it. Turning her back on the country, she goes to London to live in Gwen's flat. For only there, by getting under the skin of her sister's irregular life, does she believe she can uncover the real culprit.