The Stuart sapphire

In August 1811, George, Prince of Wales and the Prince Regent, returns to his bedroom after dinner, hoping to himself that the woman in his bed has gone home. But he is horrified to find Sarah, Marchioness of Creeve, still there-dead, strangled by the string of pearls around her neck. The Prince realises what a scandal could come out of a dead married woman (not to mention his younger brother's mistress) in his royal bed, so he has Tam Eildor, masquerading as a Scottish lawyer, investigate the murder.