When Last I Died — Gladys Mitchell

Mrs. Bradley has dealt with murderers before, but she has always dealt with them as a professional psychologist--coolly, scientifically, almost flippantly. Now, however, the brilliant old lady is fiercely determined to bring a cruel and ruthless murderer to bay. Various members of the Bradley household play significant roles in a case involving a special school where youthful offenders are sent in hopes of reforming them. First published in 1941.