Horizon investigates a new era of Alzheimer's research, which is bringing hope to millions across the world. New scanning and gene technology is allowing scientists to identify the disease at its earliest stages, often 15 years before symptoms appear. A series of new drugs trials in Colombia, the USA and Europe are showing startling success in reducing beta amyloid, the protein which is a hallmark of the disease. It is becoming clear that changes in lifestyle can prevent the development of the disease. A new system inside the brain has been discovered which clears amyloid when we are in deep sleep, but allows it to accumulate if we don't sleep well. The programme reveals that for sufferers in the early stages of the disease, brain connections can be strengthened and even replaced by absorbing enough of the right nutrients. In an ageing world, where the biggest risk of developing Alzheimer's is old age, these scientific breakthroughs are bringing hope where once there was despair.