Of all the many things humans rely on plants for, the most curious is our use of them to change consciousness: to stimulate, calm or alter the qualities of our mental experience. In a unique blend of history, science, memoir and reportage Pollan explores three very different drugs - opium, caffeine and mescaline - and throws the fundamental strangeness of our thinking about them into sharp relief. An exploration into the powerful human attraction to psychoactive plants.