The House Without the Door: Henry Gamadge #4

Acquitted of murdering her husband, Mrs. Vina Gregson remains essentially a prisoner, trapped in her elegant New York apartment with occasional furtive forays to her Connecticut estate. A jury may have found her innocent, but Mrs. Gregson remains a murderess in the eyes of the public and of the tabloid journalists who hound her every step. She has recently begun receiving increasingly menacing letters written, she is certain, by the person who killed her husband. Taking the matter to the police would heighten her notoriety, so she calls on Henry Gamadge, the gentleman-sleuth who is known for both his discretion and his ability to solve problems that baffle the police.