Navigation is the key human skill. It's something we do everywhere, whether feeling our way through a bedroom in the dark, or charting a ship's course. But how does navigation affect our brains, our memory, ourselves? In 1844, Foy's great-great grandfather, captain of a Norwegian cargo ship, perished at sea after getting lost in a snowstorm. Foy decides to unravel the mystery by re-creating his ancestor's trip using only period instruments. At the heart of Foy's story is this fact: navigation and the brain's memory centres are inextricably linked. As Foy unravels the secret behind Halvor's death, he also discovers why forsaking our navigation skills in favour of GPS may lead not only to Alzheimers and other diseases of memory, but to losing a key part of what makes us human.