The Mystery of the Spanish Chest

A woman asks Poirot to protect her from her husband, which is a request that tends to end badly no matter how carefully it is handled. Marguerite Clayton (Caroline Langrishe) lives in fear of Edward Clayton (Malcolm Sinclair), and Poirot agrees to help. Caroline Langrishe gives Marguerite a fear that feels lived-in rather than performed, which makes what happens next land harder. And then the shape of the case flips. The violent husband becomes the victim, found dead in circumstances gruesome enough to make the newspapers uncomfortable. The man everyone wanted protection from turns out to be the one who needed it, and the protection case becomes a murder case without a clean starting point.

The investigation gathers the usual circle: Colonel Curtiss (John McEnery), Major Rich (Pip Torrens), Lady Chatterton (Antonia Pemberton), Burgoyne (Peter Copley), Smithy (Sam Smart), each with a view of the marriage and an opinion about the corpse. John McEnery's Colonel Curtiss is the sort of friend who offers advice nobody asked for and nobody ignores. Hastings accompanies Poirot, Japp handles the official machinery, and the Spanish chest of the title sits at the centre of the whole business. It is a handsome, ominous object, and the camera keeps coming back to it.

Anthony Horowitz wrote it with Agatha Christie, and Andrew Grieve directed. It is a domestic story with a violent heart, and the series handles the ugliness without turning it into spectacle.

There is something queasy about watching a fear-of-the-husband case turn into a husband's murder, and the episode knows it. Poirot untangles who did what, and the answer makes sense of the opening in a way you do not see coming. The chest earns its place in the title. The Spanish Chest is not the most famous Poirot story, but it is one of the most uncomfortable, and the discomfort is the point.