The Case of the Anxious Aunt(1996)
(The ninth book in the Paula Glenning series)
A novel by Anna Clarke
When her Aunt Isabel claims that her nurse is trying to blackmail her and that her husband is attempting to poison her, Paula Glenning does not believe her, but her opinions change after the brutal murder of the nurse, and Paula must find a killer.
Used availability for Anna Clarke's The Case of the Anxious Aunt
May 1996 : USA Mass Market Paperback