"The ABC Murders" is a detective novel by Agatha Christie featuring the famous Belgian detective Hercule Poirot. The story revolves around a series of murders that follow an alphabetical pattern, with each victim's name and location corresponding to the letters of the alphabet. Poirot receives a mysterious letter from the killer, taunting him and challenging his investigative skills. As the plot unfolds, Poirot, along with his friend Captain Hastings, works to decipher the clues left by the murderer. The novel explores themes of justice, human psychology, and the nature of evil, culminating in a surprising revelation about the identity of the killer.