The Lost Mine

A Chinese-American businessman travels to London to sell a map said to be valuable, and vanishes. The map is tied to a lost mine, which is the sort of treasure that makes men behave badly, and Poirot is called in to find out where the seller went and who wanted him gone. The money involved is enough to bring out the worst in respectable people, which is Poirot's speciality.

The oddest clue in the case arrives by way of a board game. A game of Monopoly sets Poirot thinking about London's streets, and the realisation follows that some of them require a different kind of skill to read than the property deeds suggest. The map's disappearance and the man's disappearance are connected, but the connection takes some walking to find. It is a gloriously silly way to crack a mystery, and the episode has the confidence to play it straight. Around the case circle Lord Pearson, Charles Lester and his wife, Reggie Dyer, the mysterious Vincent Wong, and a hotel lobby clerk with a good memory.

Michael Baker, David Renwick and Agatha Christie share the writing credit, with Edward Bennett directing. Anthony Bate plays Lord Pearson, Colin Stinton is Charles Lester, Barbara Barnes plays Mrs Lester, James Saxon is Reggie Dyer, Vincent Wong is the Chinaman and Richard Albrecht is the lobby clerk. David Suchet, Hugh Fraser, Philip Jackson and Pauline Moran are in the usual places.

The Lost Mine is a modest mystery, and the show wisely leans into the modest. A missing man and a game of Monopoly, with the solution arriving from an unexpected corner of London. Not every case needs a body count to be worth Poirot's time, and this one proves it. It is the sort of episode that rewards a second viewing, once you know which streets to watch.