The Valley of Fear. Sir Arthur Conan Doyle

Sherlock Holmes is intrigued and disturbed when he receives an ominous coded message: a Mr. Douglas of Birlstone House is in terrible danger. Before Holmes can act, shocking news arrives. Douglas has been found dead - his face blown off by a shotgun. Scotland Yard is stumped. Was this suicide or murder? But Holmes is in no such doubt - for he recognises the calling card of his nemesis, Professor James Moriarty.