Despite his reluctance to be a pushover for every waif and stray, Larry agrees to find the sister of a fifteen year old boy who turns up at his office. Having run away from parents that he claims are abusive, he and his sister had been living rough until she disappeared.
Larry visits the boy's parents, in Cromwell's Seat, a village some ten miles outside of London, only to hear that MI6 are investigating suspected espionage centred on the local police station.
Dragged reluctantly into that investigation, while trying to solve the disappearance, he is suddenly arrested when the boy's mother is found hanged from the seventh tower of a series of fifteen carrying new power lines.
The situation is becoming difficult until Clare Haines, a constable working for his friend Superintendent Blake Reece, comes to his aid, and he is released.
The murder of a constable in an unusual manner, a face seen, and vaguely remembered, an MI6 agent who is not quite as he appears to be, a reluctant traitor, the almost fatal shooting of Penny and the death of someone who had come to be his friend, finally brings everything to a head at the foot of the tower.