But Why Bump Off Barnaby?

Barnaby Folcey is murdered at a family gathering. But while he had a motive to murder everybody else, no-one had any motive for doing away with Barnaby, and his dying clue could implicate everyone in the room. While the bizarre group frantically tries to unmask the murderer, people vanish, poison is found in the sherry, and the police take forever to arrive. Meanwhile, there's a secret treasure to be found, a mystifying limerick to decode, and all sorts of doom to be avoided before the killer is finally unmasked.