Before Miss Marple there was Amelia Butterworth!
The curious Miss Butterworth, a spinster "of Colonial ancestry and no inconsiderable importance in the social world", and "who has never experienced the doubtful bliss of marriage" lives alone in Manhattan's exclusive Gramercy Park. That Affair Next Door sees her being awakened by strange sound in the supposedly empty house next door and then its discovered that a mysterious murder has occurred there.
The inquisitive middle-aged spinster gets directly involved and though Detective Ebenezer Gryce leads the murder investigation, Miss Butterworth, undertakes her own search to try and unravel the mystery.
The novel effectively justifies Green's title as the mother of the American mystery novel, with its complex mystery plot, portrays intriguing characters, unexpected twists and keeps the reader on their toes until the very last page.