A mid-air explosion, and a plane plunges to disaster from the Scottish skies, with the British and American Defence Secretaries among the victims. Out of the blue, Edinburgh's Deputy Chief Constable Bob Skinner finds himself leading the greatest investigation of his career. The means of destruction is apparent from the start, but the investigation quickly grows more puzzling - for once, they have an embarrassment of suspects with motive and opportunity. Then sudden random violence wrenches Skinner himself out of the picture. While his colleagues struggle with the mass of clues, he lies on the brink of death, trapped with the horrors from his own hidden past. As Skinner's ordeal reaches its crescendo, the police pursue their suspects one by one, until at last they are brought to a dramatic, thrilling, but tragic conclusion.