That Affair Next Door

That Affair Next Door is a detective novel written by Anna Katharine Green and first published in 1897. It introduces the sharp-witted amateur investigator Amelia Butterworth.

After noticing a man and a young woman enter the supposedly vacant mansion next door, Amelia becomes involved when the woman is later found dead beneath an overturned cabinet. Evidence soon reveals that the incident was not an accident but a carefully concealed murder.

Convinced that her observations are essential to the case, Amelia conducts her own investigation while working alongside—and frequently competing with—police detective Ebenezer Gryce. Together they examine contradictory testimony, suspicious behavior, and physical clues that raise troubling questions about the victim’s identity.

Combining an intricate mystery with humor and social commentary, the novel presents a battle between professional detection and amateur intuition. It is also an important early example of the female amateur sleuth in American detective fiction.

"I am not an inquisitive woman, but when, in the middle of a certain warm night in September, I heard a carriage draw up at the adjoining house and stop, I could not resist the temptation of leaving my bed and taking a peep through the curtains of my window."