Robert Louis Stevenson''s strange and sinister tale of the gentle Dr Jekyll and the sadistic Mr Hyde is filled with oddities suggesting a dark reality behind a classic fiction. That dark reality is laid bare in the casebook of Inspector Swain. The ''parliamentary murder'' of 1884 leads the inspector and his portly sergeant Lumley from plush drawing-room to madhouse cell in search of the link between a coward in the red-coated ranks at Isandhlwana a killer in Cheyne Walk and the satanic persona of Edward Hyde.