When a young boy (Jon Whiteley) accidentally shoots a playmate with a pistol found in the rubble of a bombed-out building, he runs away from home and wanders the streets of postwar England. Ballistic analysis connects the weapon to the unsolved murder of a military officer ten years earlier. A gruff American captain, Mark Andrews (Steve Cochran), attempts to track down the missing gun, while trying to appease the boy's anxious mother (Lizabeth Scott). The search for the missing boy (and the weapon he's carrying) leads Andrews into the seedy London underworld, where a series of unsavory characters attempt to divert him from his quest. As depicted by director Val Guest the decayed urban setting resembles the Vienna of Carol Reed's THE THIRD MAN, permeated by grime and shadow, and shot through with an oppressive sense of despair.