Charles Nesbitt, an expert on chemical weapons, threatens to contaminate the water sources of London with a lethal hallucogenic drug and in order to back up his claims, plans several small 'demonstrations' in warning to the local authorities - including CI5.

A CI5 agent is murdered, leading to the discovery of a man who is dying as a result of plutonium poisoning. This links CI5 to a further plot involving the imminent explosion of an A-bomb at the same bowling alley. It's left to Bodie and Doyle to try and de-activate the fuse before it takes them and the whole of London with it.

A suspect being held under CI5's supervision is found dead in his cell - apparently after a fatal blow administered by Doyle. A public inquiry ensues and an influential lawyer calls for CI5 to be shut down. It's left to Cowley in fighting to save the organisation he founded.