There is to be a big CND demonstration outside the Fylingdales early warning defence base near Aidensfield, and prospective MP - Paul Melthorn is to make a speech there. Workers take offence when demonstrators are putting up posters everywhere advertising the demo and Nick has to break up a row in the pub between them. In doing so one of the demonstrators gets injured and Nick gets accused of assaulting him. Ashfordly police in the meantime are informed to police the demo and Blaketon finds out that the American Ambassador is visiting Fylingdales at the time of the demo. The demonstrators campsite is then burgled and Melthorn's wallet, which contains incriminating pictures of him having an affair with a young woman are stolen. The demo takes place and the road is blocked with demonstrators. Melthorn makes his speech but becomes ill and Kate arrives to treat him and discovers he has a weak heart. It turns out that the demonstrator who accused Nick of assault is in fact a Special Branch