A Most Mysterious Murder

The Case of the Croydon Poisonings (1x4)

: 30, 2005

1929. Three members of a respectable middle-class family, all living along the same street, die one after the other. The first two deaths are incompetently put down to "natural causes" by the local quack. But the third starts to cause a scandal. Exhumations reveal arsenical poisoning in all three. Who among the remaining members or close associates was the murderer?