While on the way to work, secretary Pat Hunnisett takes a free promotional chocolate from a group of girls on the street. Meanwhile, at the Doomwatch office, Quist and his team are investigating the sudden increase in the country's smokers, and are surprised when Pat arrives and lights up a cigarette for the first time in five years. Quist suspects that there could be a link between the promotional chocolates and 'Checker Board' cigarettes, whose recent sales are doing unexpectedly well. Should subliminal advertising be allowed?

The Doomwatch team look into serious health issues experienced by male workers at a Welsh battery farm.

A powerful antidote formula has been stolen near a school full of gifted boys. Are they responsible, and is computer technology somehow to blame?