It is January 1719 and Daniel Defoe, almost sixty, sits at a table, writing. He is troubled with gout and debt, but for now is preoccupied with a younger man on a barren shore – Robinson Crusoe, for which he will principally be remembered. Several miles south, an old man, Robert Knox, is bent over a heavy volume. It is Historical Relation, his account of being held captive on Ceylon, published forty years ago after he escaped and returned to England. It has long been out of print, but a copy perhaps sits on the desk of Daniel Defoe as he writes. Where did Crusoe come from? And what is the secret of his endurance? Crusoe explores the intertwined lives of two real men – Daniel Defoe and Robert Knox – and the character and book that emerged from their peculiar conjunction. It is the biography of a book and its hero, the story of Defoe, the man who wrote Robinson Crusoe, and of Robert Knox, the man who was Crusoe.