Divisional Detective Inspector Harry Labar, professionally indolent but observant, is pressed to tighten a crime-ridden district while a sophisticated, untraceable criminal operator hovers beyond suspicion. A mysterious hundred-pound note delivered by a woman in a motor car sparks an inquiry that draws Labar into intersections of high society, shady financiers, and organised thieves. The narrative follows his methodical detective work, the bureaucratic and personal pressures he faces, and the gradual unraveling of a network that profits from polished respectability, combining procedural detail with suspense and social observation.