A particularly vicious serial killer is stalking the Norfolk coast in the vicinity of the Larksoken nuclear power station. The press have branded him 'The Whistler' because witnesses have heard a hymn being whistled in the vicinity of the murders. His trademark is the letter 'L' carved on the forehead of his victims. L for Larksoken? At first, his victims seem to be chosen entirely at random - women in the wrong place at the wrong time - but then two women employed at the nuclear power station are murdered in quick succession...