Running through the heart of Colombia is the Magdalena, a river emblematic of the fascination and tragedy of South America. Considered by some to be the most dangerous place in the world, the riverbanks are home to a group of townships with the world’s highest incidence of early onset Alzheimer’s. In 2011, Michael Jacobs travelled its length and here he recounts his journey through a heartland of mystery, magic and darkness and reflects on the lives of his parents – sufferers from Alzheimer’s and dementia – and our experience of memory.