Appointment with Death

Mrs. Boynton is one of Christie's most genuinely sinister creations — a tyrannical stepmother who has psychologically crushed her adult children into helpless dependence. When she turns up dead from a mysterious injection at the ancient city of Petra, Poirot has 24 hours to unravel which of her exhausted family members finally acted. This one is less about the puzzle mechanics than it is about the psychology of abuse and control, and Christie renders the family's suffering with unusual care. The atmospheric Petra setting is vivid and memorable. The honest caveat is that Christie scholars are divided on the solution — some consider it among her weaker resolutions, and the supporting characters exist mainly as victims rather than fully realized people. Strong on atmosphere and psychology; the whodunit mechanics don't quite match.