Episode aired Oct 30, 1983
Death is like a box of chocolates
Agatha Christie's "The House of Lurking Death" was adapted by Jonathan Hales.
Lois Hargreaves (Lynsey Baxter) receives a box of chocolates. She naturally shares them with others later to find that the chocolates were laced with poison. Not enough to kill but to make everyone sick. Being private and figuring that the anonymous chocolates came from someone in that very house. Mary contacts Mr. Blunt (James Warwick) and Miss Robinson (Francesca Annis) of the International Detective Agency.
Naturally, as with their first two episodes or movies, Tommy and Tuppence are both wise beyond their time and do some of the dumbest things that lead them to the solution of the problem. Will they be there in time to save Mary or if not, will they be able to figure out who and how it was done. More important why.
As with most of the Partners in Crime series we are far ahead of them on the whom. The fun is to watch them figure out not only the why but the other details. This story is a period piece of just after The Great War.