Great Mistake, The by Mary Roberts Rinehart, Otto Penzler (Introduction); 1940/2023. Softcover.

In an elaborate house known as the Cloisters, Maud Wainwright rules supreme. The queen of society in the small town of Beverly, she has a table long enough to seat one hundred, and she keeps an iron grip on the guest list. Her right-hand woman is Pat Abbott, a local girl who is beautiful, innocent, and kind. Pat has no idea how cutthroat high society can be, but she's about to get a deadly first lesson.

Pat has fallen head over heels in love with Maud's son, Tony, a clever young rake with a single flaw: his vicious, gold-digging wife. At the same time that she is dangerously infatuated with a married man, Pat's world is turned upside down by a series of attacks on the estate--and a truly shocking murder. To save Tony and Maud, Pat must find the killer.

But the list of suspects is as long as one of Maud's guest lists: When a woman has room at her table for one hundred friends, she'll have more than her share of enemies.