In a compelling and at times disturbing series, Dr Michael Mosley explores the brutal history of experimental psychology. To begin, Michael traces the sinister ways this science has been used to try to control our minds. He finds that the pursuit of mind control has led to some truly horrific experiments and left many casualties in its wake. Extraordinary archive captures what happened - scientists systematically change the behaviour of children; law abiding citizens give fatal electric shocks; a gay man has electrodes implanted in his head in an attempt to turn his sexuality. Michael takes a hallucinogenic drug as part of a controlled experiment to try to understand how its mind-bending properties can change the brain. This is a scientific journey which goes to the very heart of what we hold most dear - our free will, and our ability to control our own destiny.