The main protagonist of River of Darkness is a Scotland Yard detective so damaged by his experiences during the First World War that his superiors worry about his ability to do his job. This may sound like Charles Todd's excellent series about Ian Rutledge, a shell-shocked cop from the same era. But Rennie Airth, a South African journalist who lives in Italy, has made his hero--Inspector John Madden--a somewhat different version of one of England's walking wounded. Madden is both gloomier (he lost his wife and young daughter to an influenza epidemic) and more pragmatic than the poetic, indecisive Rutledge.
Madden is sent to a town in Surrey where a local family has been massacred in what looks like a robbery gone wrong. He finds enough echoes of his recent battlefield experiences to conclude that the killer was just one man--most likely a former soldier using a bayonet. As for motive, it could well be perverse sexual passion, that "river of darkness" to which a psychologist introduces him. We meet the killer early on, watch him as he maintains a rigid control over every aspect of his life, then stare in horror as he periodically explodes into mad violence. Unlike Madden, this man has not been severely damaged or changed by the war; he has simply used it to channel and redirect his dark river. Airth's point--that survival comes in many shapes and sizes--gives a solid foundation to an impressive leap of imagination.