Elephants Can Remember

Two investigations run side by side, and the episode is better for it. Poirot is looking into the murder of a renowned psychiatrist, a case that should be straightforward and is not. Ariadne Oliver, meanwhile, has been set a task by her goddaughter: find out the truth behind the mysterious deaths of her parents, General and Lady Ravenscroft, years before. The psychiatrist's murder pulls Poirot in; the Ravenscroft question pulls Oliver. Neither of them knows how much they need each other.

Oliver's method is memory. She goes from person to person, asking what they remember about the Ravenscrofts, collecting impressions the way elephants are said to collect theirs. Mrs Burton-Cox remembers one thing, Doctor Willoughby another; Detective Inspector Beale, Marie, Celia Ravenscroft and Julia Carstairs all have their versions, and the gaps between them are where the truth hides. Poirot works his own case with his own discipline, but the episode keeps coming back to the simple idea that people remember imperfectly, and that imperfection is a kind of evidence.

Nick Dear wrote the adaptation with Christie, and John Strickland directed. Vanessa Kirby is a striking Celia Ravenscroft, with Adrian Lukis and Annabel Mullion as the dead parents, Greta Scacchi as Mrs Burton-Cox, Iain Glen as Doctor Willoughby, Vincent Regan as Detective Inspector Beale, Alexandra Dowling as Marie and Caroline Blakiston as Julia Carstairs.

This is a quieter Poirot than usual, more about listening than deduction, and the pairing with Oliver gives it a warmth the harder cases lack. She is allowed to be wrong, vague and human, and the contrast with Poirot's exactness is the whole pleasure. The episode earns its title: every answer comes from somebody's memory, and every memory arrives with a slant of its own.

It is not the flashiest case of the final season, but it may be the kindest. And for a series saying goodbye, a story about remembering things properly feels exactly right.