The Theft of the Royal Ruby

A royal ruby disappears over the Christmas holidays, stolen with a cheek that borders on insult from Prince Farouk (Antony Zaki), and Poirot is asked to get it back. Christmas, in this series, is rarely peaceful for long. He agrees reluctantly, which is his way of agreeing at all. The theft is brazen enough to be a message, and the prince wants his jewel back before anyone has to explain to the wrong people how it vanished. A ruby that belongs to a prince is a diplomatic incident with a price tag.

The case keeps Poirot close to home, among the Laceys: Colonel Lacey (Frederick Treves), Mrs Lacey (Stephanie Cole), their daughter Sarah (Helena Michell). Around them move Desmond Lee-Wortley (Nigel Le Vaillant), David Welwyn (John Vernon), Jesmond (David Howey), Gloria (Robyn Moore) and Peverill (John Dunbar), a gathering small enough that every conversation feels like it might be the one that gives the game away. Frederick Treves and Stephanie Cole make the Laceys a proper household, polite on the surface and watchful underneath.

Anthony Horowitz and Clive Exton wrote it with Agatha Christie, and Andrew Grieve directed. It is a Christmas episode in the best tradition: festive on the surface, thievery underneath, and nobody quite telling the truth about the turkey. The two get along better than they should.

The pleasure is in the smallness. The scale is small: one gem, one house, a family and its guests. The theft grows more embarrassing the longer it stays unsolved, and Poirot looks where everyone else has already looked and sees what they missed. The ruby comes home in time for the season's goodwill, and everyone pretends the whole thing never happened, which feels about right for Christmas. It is a cosy episode with sharp corners, and the sharpness is what makes it worth revisiting.