Always fascinated by islands, Oliver Sacks is drawn to the Pacific by reports of the tiny atoll of Pingelap, with its isolated community of islanders born totally colour-blind; and to Guam, where he investigates a puzzling paralysis endemic there for a century. Along the way, he re-encounters the beautiful, primitive island cycad trees - and these become the starting point for a meditation on time and evolution, disease and adaptation, and islands both real and metaphorical.