From back cover:
> Penny is looking forward to a lengthy
> visit from her son, Dr. Alex Spring,
> when she receives a summons from
> Scotland Yard. Where is Sir Tobias
> Glendower? It happens that a young
> Russian ballerina is being held in
> custody as primary suspect in the
> bizarre bludgeoning-to-death of one of
> the members of a visiting Soviet
> corps de ballet. But she will speak only to Sir Toby, who she claims is her father! Toby is eventually reached
> at his private archeological
> excavation deep in the Welsh
> countryside - the "folly" of the title
> - and plunged headlong into mayhem and danger.