Anna Katharine Green 
Mayor’s Wife [EPUB ebook] 

Miss Saunders, a discreet domestic spy of some kind, is hired by Mayor Packard to look after his unaccountably abstracted wife whilst he goes out of town for a fortnight. The house the couple have been renting during the mayor’s election push is reputed to be haunted. Its past contains the story of a death and a lost fortune, while recent tenants have left in a hurry after reporting strange disturbances. (Goodreads)