Sun, Mar 1, 1970
Doomwatch are alerted to reports of a number of attacks on humans by rats. Toby and Bradley investigate the house of Mr. and Mrs. Chambers, victims of a recent attack; the two scientists lay traps in the kitchen, but the rodents display unusual intelligence by jamming the traps open using cutlery found on a worktop, and then viciously attack the men. Meanwhile, Ridge becomes involved with Doctor Mary Bryant, who has been conducting experiments on a group of rats in a room in her flat - but the rats have managed to escape, and have now turned carnivorous.
Sun, Mar 8, 1970
Doomwatch are joined by Doctor Robson, sent to undertake tests on the new 'Sahara' spray which is apparently capable of destroying all plant-life on the planet. But when Quist receives a phone call from the ministry, he is given orders to immediately suspend both Robson and Toby without any explanation. Closer investigation leads Quist and his team to discover that a new computerised security system run by Commander Keeping and Barker has become far too powerful, and is making its own decisions about government personnel.
Sun, Mar 22, 1970
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?