Season 4

The ' polygraph' lie-detector has arrived in Britain. It measures tiny changes in your breathing, perspiration, and heartbeat, as they ask you questions. Someone's hurt - did you do it? Did you steal money from the till? Did you lie when applying for your job? Q.E.D. observes the polygraph in action in America, sees a British ex-policeman in training in Atlanta, and meets a man found guilty of murder after a polygraph test. In Britain, we may soon rely on it for our national security. But is that wise? How does the polygraph work? How effective is it? Can you beat it? And who's next for the little test - could it be you?

Both Tim and Jean Richardson - from East Grinstead - are ' professional parents', formally approved by the Better Baby Institute in Pennsylvania, USA. They have three children: Rufus, 5, has ' a rage to learn Beth, 3, ' would rather learn than eat'; and Harry, at 18 months, ' would much rather learn than play'and yet they are all perfectly ordinary, happy children. What's the trick? Well, Q.E.D. followed a group of learner parents through their one-week course in Pennsylvania. After all, says Glen Doman , the founder and force behind the institute, ' a child's brain is the only container that the more you put into it, the more it will hold '.

In this programme, HEINZ WOLFF steps aboard a London bus and finds himself immediately transported to a bizarre and unfamiliar world. The past. The year 1948. As he wanders round that strange era of de-mob suits, Clement Attlee , Victor Silvester and Snoek, he asks: ' What has technology actually done for our lives? How different are our homes, our clothes, our food?' What has really changed since 1948, the year when George Orwell wrote Nineteen Eighty Four? His journey takes him past East End hop-pickers and to the waiting BEA Dakota sitting on the tarmac at Northolt, its engines revving for the flight to Paris - a weekend treat for the well-to-do!

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The Bat, the Blossom and the Biologist with Donna Howell There is in Arizona a bat that flies thousands of miles each spring to feed on the flowers of a plant that blooms only once in 25 years-and then dies. Last summer Q.E.D. went to the Sonoran Desert in pursuit of this curious but intimate relationship-for it is a trading of food for sex: the bat gets the food and the flower gets pollinated in exchange. How did such a partnership ever come about? For more than a decade biologist DONNA HOWELL has been unravelling just why two such unlikely partners got together and how they make the most of each other.

Would you make a good eye-witness? Here's your chance to find out with some experiments that could change your mind. The evidence shows we can recall events that never happened. And recognise people that we have never seen. So Q.E.D. asks how far can we trust the evidence of eyewitnesses in the practical business of crime?