Elizabeth Daly 
The House Without the Door [EPUB ebook] 

Vina Gregson needs help. Finally acquitted of the murder of her husband, who died from a probably-not-accidental overdose, she had money and the will to spend it. But the eyes of the world still see her as a murderer, acquitted or otherwise. And someone has started to do something about it.

Threatening messages and four attempts at her life later, she calls in amateur investigator Henry Gamadge to find the person responsible. But while he has his theories, it is not long – actually, it does take a while to be honest – before someone lies dead. Can Gamadge find the murderer before their plans reach fruition?