Light ThickensThe complete series of Ngaio Marsh reissues concludes with the re publication of this 20th anniversary edition of Light Thickens, her final novel. Peregrine Jay, owner of the Dolphin Theatre, is putting on a magnificent production of Macbeth, the play that, superstition says, always brings bad luck. But one night the claymore swings and the dummy's head is more than real: murder behind the scene. Luckily, Chief Superintendent Roderick Alleyn is in the