Elephants Can Remember by Agatha Christie

Hercule Poirot is asked to solve a decades-old mystery involving the mysterious death of a married couple. With only fragmented memories from elderly witnesses—people who may remember more than they realize—Poirot works alongside Ariadne Oliver to reconstruct the past. As he pieces together conflicting accounts, he discovers how memory, time, and truth can blur into a dangerous puzzle where even forgotten details can unlock a hidden crime.