This carefully plotted tale of the investigation into a small boy’s death is a compelling, psychologically astute watch – which constantly pulls the rug out from under you This carefully plotted tale of the investigation into a small boy’s death is a compelling, psychologically astute watch – which constantly pulls the rug out from under you B y ’eck – it’s grim out west. Such is the overriding impression wrought by Under Salt Marsh, a six-part crime drama set in the fictional Welsh town of