The Hand in the Dark - Arthur J. REES

An ancient English country house with a storied and bloody history is the setting for this intriguing mystery. It is the autumn of 1918. The War to End All Wars is still raging in Europe, but in this peaceful setting a bored young wife hosts a party for friends from London, including war workers, servicemen, and a famous explorer and expert on jewels. Hours later she is dead of a gunshot wound, an heirloom pearl necklace is missing, and Scotland Yard is homing in on possibly the wrong suspect. Can the famous private detective Mr. Colwyn bring the murderer to justice? - Summary by Jacquerie